# coldletter.com


## Posts

- [Why Gmail Isn't Showing the Unsubscribe Button (and How to Fix It)](https://coldletter.com/blog/gmail-unsubscribe-button-not-showing/): Gmail shows its native unsubscribe button only when a message passes Google’s automated eligibility checks, and a List-Unsubscribe header is just one of those checks, not a guarantee. Per Google’s own sender guidelines FAQ, “unsubscribe buttons or links are displayed at the top of messages (next to the sender name) only for messages that pass […]
- [PTR Records for Email: What They Are and Why They Matter (2026)](https://coldletter.com/blog/ptr-record/): A PTR record maps a sending IP address back to a hostname, the reverse of what an A record does. Here is how reverse DNS and the FCrDNS check work, why Gmail and other mailbox providers require a valid one, who actually controls it, and how to set and verify yours.
- [Best Customer.io Alternatives (2026)](https://coldletter.com/blog/customer-io-alternatives/): Customer.io alternatives compared: Braze, Iterable, Encharge, Loops, Brevo, and MailerLite, with verified pricing, fit, and where each falls short.
- [Best Litmus Alternatives for Email Testing (2026)](https://coldletter.com/blog/litmus-alternatives/): Litmus quietly moved its Plus plan to a $500/month Core tier in August 2025, a roughly 151% increase, and stopped publishing self-serve pricing beyond it. Here are seven alternatives for teams re-evaluating their email QA stack, from like-for-like preview suites to developer-first testing tools.
- [Amazon SES vs SendGrid: Cost, Deliverability, and Setup (2026)](https://coldletter.com/blog/amazon-ses-vs-sendgrid/): At 100,000 emails/month, SES costs ~$10 and SendGrid costs $34.95-$89.95. See the full pricing, deliverability, and setup comparison.
- [SendGrid vs Mailchimp: Transactional vs Marketing Email (2026)](https://coldletter.com/blog/sendgrid-vs-mailchimp/): SendGrid vs Mailchimp compared for 2026: pricing, deliverability, API depth, and marketing automation, with a clear verdict by use case.
- [Resend vs SendGrid: Transactional Email Compared (2026)](https://coldletter.com/blog/resend-vs-sendgrid/): Resend and SendGrid both send transactional email reliably, but they come from different eras of tooling. A side-by-side on DX, React Email, pricing, and deliverability, verified as of July 2026.
- [Best Email Deliverability Tools for 2026](https://coldletter.com/blog/email-deliverability-tools/): A roundup of email deliverability tools by category: seed testing, reputation monitoring, DMARC management, and warmup, with pricing verified July 2026.
- [Best Constant Contact Alternatives (2026)](https://coldletter.com/blog/constant-contact-alternatives/): Constant Contact's per-contact pricing climbs fast and its automation stays newsletter-first. Compare 8 alternatives with July 2026 pricing and how to pick one.
- [Best Klaviyo Alternatives (2026)](https://coldletter.com/blog/klaviyo-alternatives/): Best Klaviyo alternatives for 2026, compared for ecommerce and SaaS teams: Omnisend, Drip, Brevo, Customer.io, MailerLite, and more, with current pricing.
- [How to Add an Unsubscribe Link (and Why It’s Required)](https://coldletter.com/blog/unsubscribe-link/): When an unsubscribe link is legally required under CAN-SPAM and GDPR, how it relates to the List-Unsubscribe header, and how fast you must honor requests.
- [Receipt Emails: What to Include, Best Practices, and a Template](https://coldletter.com/blog/receipt-email/): A receipt email confirms a payment succeeded and gives the customer a record of it: the amount, the date, a transaction ID, the payment method masked to the last four digits, and a support contact. This guide covers the required fields, how fast to send it, marketing-content limits, and a copy-paste template.
- [SMTP Error 550: What It Means and How to Fix It](https://coldletter.com/blog/smtp-550/): A 550 SMTP reply means the message was permanently rejected. Here is what the common variants (5.1.1, 5.7.1, 5.7.26, and more) mean, how to tell whether the problem is on your side, and how to fix each one.
- [Catch-All Email Addresses: What They Are and Their Deliverability Risks](https://coldletter.com/blog/catch-all-email/): Catch-all domains accept every address a server checks, so verifiers report unknown instead of valid, and why that raises bounce risk.
- [Best Transactional Email Service According to Reddit (2026)](https://coldletter.com/blog/best-transactional-email-service-reddit/): Ask Reddit for the best transactional email service and the same short list comes back: Postmark for deliverability, Resend for developer experience, and Amazon SES for cost at scale.
- [Dedicated IP vs Shared IP for Email: Which Should You Use?](https://coldletter.com/blog/dedicated-ip-vs-shared-ip/): A dedicated IP puts your sender reputation entirely in your own hands, but it only pays off past a certain volume. Here's how ESPs define that threshold, and a framework for choosing between the two.
- [Email Deliverability Rate: How to Measure and Improve Inbox Placement](https://coldletter.com/blog/email-deliverability-rate/): Email delivery rate and deliverability rate measure different things: one tracks server acceptance, the other tracks inbox placement. Here is how each is calculated, how to measure inbox placement rate directly, and what the 2026 benchmark numbers actually mean.
- [Email Conversion Rate: How to Measure and Improve It](https://coldletter.com/blog/email-conversion-rate/): Email conversion rate measures how many recipients complete an action, not just click a link. Learn the formula, how it differs from CTR, real benchmarks by send type, and why open-based tracking distorts the numbers.
- [Email Warmup on Reddit: What Actually Works According to Users](https://coldletter.com/blog/email-warmup-reddit/): Reddit's take on email warmup is more balanced than the tool vendors suggest: it helps a new domain, but it will not save bad copy, weak targeting, or a reputation that is already damaged.
- [Email Click-Through Rate: Benchmarks and How to Improve It](https://coldletter.com/blog/email-click-through-rate/): Email click-through rate benchmarks from Mailchimp, Campaign Monitor, and HubSpot, the CTR vs CTOR difference explained, and the tactics that improve it.
- [GDPR and Email Marketing: Consent, Compliance, and What You Must Do (2026)](https://coldletter.com/blog/gdpr-email-marketing/): How GDPR applies to email marketing: lawful basis, valid consent, the soft opt-in exception, and how transactional email differs, plus a compliance checklist.
- [MJML: The Responsive Email Framework, Explained](https://coldletter.com/blog/mjml/): MJML compiles semantic /-style tags into the nested tables, inline styles, and Outlook conditional comments that responsive HTML email actually needs. Here's how the component model, CLI, and framework integrations work, and where MJML sits next to React Email and raw HTML.
- [Mailgun vs SendGrid: What Reddit Users Actually Say](https://coldletter.com/blog/mailgun-vs-sendgrid-reddit/): Looking for a Mailgun vs SendGrid verdict on Reddit? The honest answer is that most experienced users have moved on from both, toward SES, Resend, and Postmark.
- [Best Transactional Email APIs for Developers (2026)](https://coldletter.com/blog/transactional-email-api/): A developer-first look at transactional email APIs: authentication patterns, webhook signing, batch limits, and templating models for Postmark, SendGrid, Resend, Mailgun, Amazon SES, and Brevo, as of July 2026.
- [Best ActiveCampaign Alternatives for SaaS Teams (2026)](https://coldletter.com/blog/activecampaign-alternatives/): ActiveCampaign’s automation caps and CRM pricing push many SaaS teams to look elsewhere. Compare 8 alternatives with July 2026 pricing and how to pick one.
- [Best SMTP Provider According to Reddit (2026)](https://coldletter.com/blog/best-smtp-provider-reddit/): Reddit does not crown one best SMTP provider, but a few names dominate the threads: Amazon SES for a cheap reliable endpoint, Postmark for deliverability, and self-hosted Postal for the hands-on crowd.
- [MailerLite Pricing Explained: Plans, Limits, and Costs (2026)](https://coldletter.com/blog/mailerlite-pricing/): MailerLite's Free, Comfort, Power, and Enterprise plans compared: 2026 starting prices, subscriber-based billing, send limits, and the June price hike.
- [AMP for Email: What It Is, How It Works, and Should You Use It](https://coldletter.com/blog/amp-for-email/): AMP for email adds interactive components, forms, carousels, live pricing, to messages in Gmail, Yahoo Mail, and Mail.ru. Here is the MIME structure, the sender registration requirement, the real use cases, and the trade-offs that determine whether it is worth building in 2026.
- [Email Regex: How to Validate Email Addresses (and Why Regex Isn't Enough)](https://coldletter.com/blog/email-regex/): The safest email regex for most applications is the one browsers already run against  fields, straight from the WHATWG HTML Living Standard. It catches malformed input, but it cannot confirm the mailbox on the other end exists, that takes a DNS lookup and an SMTP conversation.
- [Plain Text vs HTML Email: Which to Use and When](https://coldletter.com/blog/plain-text-vs-html-email/): Plain text and HTML are two different message formats, not two different reputations with mailbox providers. This guide covers when each wins, why deliverability depends on authentication and engagement rather than format, and how multipart/alternative sends both at once.
- [DKIM Selector: What It Is and How to Find Yours](https://coldletter.com/blog/dkim-selector/): A DKIM selector is the label in a DKIM-Signature header's s= tag that points a verifier to the right public key in DNS. Here's how to find yours, read a real DNS lookup, and rotate selectors without breaking signatures still in transit.
- [Email OTP: How One-Time Passcodes Over Email Work (and How to Send Them)](https://coldletter.com/blog/email-otp/): How email OTP works: code length, expiry, hashed storage, and rate limits, plus how it compares to magic links and SMS OTP for login verification.
- [Magic Link Emails: How Passwordless Login Works](https://coldletter.com/blog/magic-link-email/): A magic link email authenticates a user with a single-use, expiring token instead of a password: click the link, land in an authenticated session. This covers the token contract, the security risks unique to email-based auth, and how magic links compare to email OTP and passwords.
- [Transactional Email Examples: Types, Templates, and What to Include](https://coldletter.com/blog/transactional-email-examples/): A catalog of the 11 transactional email types every SaaS product sends, from welcome and password reset to receipts, invoices, and dunning notices, with what to include and a short example for each.
- [Invoice Emails: What to Include, Best Practices, and a Template](https://coldletter.com/blog/invoice-email/): An invoice email needs the invoice number, due date, and total due in the body itself, not just the attached PDF, plus a working payment link and a sender address someone monitors. This guide covers what to include, subject line and reminder timing, deliverability, and a copy-paste template.
- [Email Dark Mode: How to Design Emails That Look Right in Dark Mode](https://coldletter.com/blog/email-dark-mode/): Dark mode doesn’t mean one thing across email clients. Apple Mail leaves your HTML untouched, Outlook.com flips only pure black and white, and Gmail’s iOS app rewrites colors throughout the message. Here’s how to control all three with CSS and keep logos legible everywhere.
- [IP Warming: How to Warm Up a New Sending IP (Step-by-Step)](https://coldletter.com/blog/ip-warming/): A dedicated sending IP has no history, so mailbox providers judge it purely on what you do in the first few weeks. Learn the mechanics, a representative warmup schedule, and how to monitor progress on a dedicated IP.
- [Brevo Pricing Explained: Plans, Email Limits, and Costs (2026)](https://coldletter.com/blog/brevo-pricing/): A breakdown of Brevo's pricing tiers, email-volume limits, and the contact-based vs. volume-based billing distinction, verified against the official pricing page as of July 2026.
- [No-Reply Emails: Why to Avoid noreply@ (and What to Use Instead)](https://coldletter.com/blog/noreply-email/): A noreply@ sending address blocks replies, invites spam complaints, and gives up the engagement signals mailbox providers reward. Here is what the data says, the narrow cases where it still holds up, and what to use instead.
- [Mailgun Pricing Explained: Plans, Costs, and Overages (2026)](https://coldletter.com/blog/mailgun-pricing/): A breakdown of Mailgun's Free, Basic, Foundation, and Scale plans, overage rates, dedicated IP and validation add-ons, and Mailgun Optimize's separate pricing, verified against the official pricing page as of July 2026.
- [SendGrid Pricing Explained: Plans, Costs, and What to Watch For (2026)](https://coldletter.com/blog/sendgrid-pricing/): Twilio SendGrid actually sells two separate products with two separate price lists: Email API (transactional and programmatic sending) and Marketing Campaigns (contact-based email marketing). As of July 2026, Email API runs from a free 100 emails/day tier up through Essentials ($19.95/mo for 50,000 emails), Pro ($89.95/mo for 100,000 emails), and custom-priced Premier. Marketing Campaigns bills […]
- [Resend Pricing Explained: Plans, Limits, and Costs (2026)](https://coldletter.com/blog/resend-pricing/): A breakdown of Resend's pricing tiers, free tier limits, overage rates, and a worked cost example, verified against the official pricing page as of July 2026.
- [Postmark Pricing Explained: Plans, Costs, and Credits (2026)](https://coldletter.com/blog/postmark-pricing/): Postmark prices by monthly email volume, not prepaid credits: four plans from free to $18/mo, overage rates that drop as you grow, and a shared quota across transactional and broadcast streams. Here is the full structure with a worked cost example.
- [Email Bounce Rate: What Counts as Good and How to Reduce It](https://coldletter.com/blog/email-bounce-rate/): Email bounce rate measures the percentage of sent messages that failed to deliver. Learn the formula, what the thresholds mean for your sender reputation, and the concrete steps that keep your bounce rate below 2%.
- [Best Resend Alternatives for SaaS Teams in 2026](https://coldletter.com/blog/resend-alternatives/): Postmark is the top pick for inbox placement on critical transactional sends. Amazon SES wins on raw cost at volume. Brevo and Loops handle the transactional-plus-lifecycle combination. Mailtrap adds a testing sandbox alongside production sending. This guide covers seven verified alternatives with real pricing and a use-case decision matrix.
- [Password Reset Email: Best Practices, Flow, and a Template That Converts](https://coldletter.com/blog/password-reset-email/): A secure password reset email combines a single-use, time-limited token with a clear one-button message that matches your product identity. This guide covers the full flow for developers and the email mechanics for product teams, with a ready-to-adapt template.
- [Email Preheader Text: What It Is and How to Write One (With Examples)](https://coldletter.com/blog/email-preheader/): The email preheader (preview text) is the short line shown after your subject in the inbox. Learn what it is, how to write one that lifts open rates, how to implement the hidden preheader span in HTML, and see before/after examples.
- [List-Unsubscribe Header: One-Click Unsubscribe Explained](https://coldletter.com/blog/list-unsubscribe-header/): The List-Unsubscribe header is an email header field that lets mailbox providers render a native “Unsubscribe” button at the top of a message, separate from any unsubscribe link in the body. When paired with the List-Unsubscribe-Post header defined in RFC 8058, that button triggers a true one-click unsubscribe: the mail client sends an HTTP POST […]
- [Email Warmup: How to Warm Up a New Domain or IP (2026)](https://coldletter.com/blog/email-warmup/): Email warmup is the practice of gradually increasing sending volume from a new domain or IP address so that Gmail, Outlook, Yahoo, and other mailbox providers build a positive reputation for you before you send at full scale. The method: start with tens or low hundreds of emails per day to your most engaged recipients, […]
- [What Is DKIM? How It Works and How to Set Up a DKIM Record](https://coldletter.com/blog/what-is-dkim/): DKIM (DomainKeys Identified Mail) is an email authentication standard defined in RFC 6376 that lets a receiving mail server verify two things: the message was authorized by the owner of a specific domain, and the message content was not altered in transit. It does this through a public/private key pair: the sender signs outgoing mail […]
- [SMTP Ports Explained: 25, 465, 587, and 2525 (Which to Use)](https://coldletter.com/blog/smtp-ports/): Use port 587 with STARTTLS for virtually all application email submission. It is the standard submission port defined in RFC 6409 and requires authentication before accepting mail. If your network or firewall blocks 587, try port 465 (implicit TLS, re-standardized in RFC 8314) or port 2525 (a non-official but widely supported fallback). Port 25 is […]
- [SPF Record Syntax Explained: Mechanisms, Qualifiers, and the all Tag](https://coldletter.com/blog/spf-record-syntax/): A complete reference guide to SPF record syntax: version tag, mechanisms (a, mx, ip4, ip6, include, exists), qualifiers (+ - ~ ?), the -all vs ~all choice, the 10-lookup limit, and annotated real-world examples.
- [Best MailerLite Alternatives for SaaS Teams (2026)](https://coldletter.com/blog/mailerlite-alternatives/): The best MailerLite alternative depends on where the fit breaks down for your team. For transactional email, Postmark or MailerSend are the clearest upgrades. For SaaS lifecycle automation with event triggers, Loops or Customer.io handle product-driven workflows that MailerLite was not designed for. For developer teams wanting a clean sending API, Resend or Mailgun fit better. MailerLite is a solid tool for its target market; the question is whether that target market is yours.
- [What Is a Spam Trap? Types, How You Hit Them, and How to Stay Clear](https://coldletter.com/blog/spam-trap/): Spam traps are monitoring addresses used by mailbox providers and blocklist operators to catch senders with poor list hygiene. Learn the three types, how you end up hitting them, and the practical steps that keep your list clean.
- [Email Layout: Structure, Sections, and HTML Patterns That Render Everywhere](https://coldletter.com/blog/email-layout/): Learn how to structure an HTML email with nested tables, modular sections, and a ~600px wrapper so it renders consistently in Gmail, Apple Mail, and Outlook.
- [What Is an SMTP Relay? How It Works and When You Need One](https://coldletter.com/blog/smtp-relay/): An SMTP relay is a third-party service that accepts your outbound mail and handles the actual server-to-server delivery for you, including reputation management, bounce processing, and suppression lists. Here is how it works and when you need one.
- [How to Build a Responsive HTML Email Template](https://coldletter.com/blog/responsive-email-template/): A code-first tutorial covering table-based layouts, the fluid/hybrid approach, media queries, Outlook MSO ghost table caveats, and a minimal working responsive HTML snippet.
- [What Is BIMI? Brand Logos in the Inbox Explained](https://coldletter.com/blog/bimi-record/): BIMI (Brand Indicators for Message Identification) is a DNS-based standard that lets you display your company logo directly in the inbox, next to your sender name. Gmail, Yahoo Mail, and Apple Mail show a verified logo when your domain passes strict authentication checks and, in most cases, holds a cryptographic certificate proving logo ownership. The […]
- [Double Opt-In: What It Is and Why It Protects Deliverability](https://coldletter.com/blog/double-opt-in/): Double opt-in requires new subscribers to confirm their email address before joining your list. Here is how it works, when to use it, and what GDPR says.
- [Re-Engagement Emails: How to Win Back Inactive Users](https://coldletter.com/blog/re-engagement-email/): A practical guide to re-engagement and win-back email campaigns for SaaS: when to trigger, campaign structure, what to send, and when to suppress.
- [Merge Tags and Dynamic Email Content Explained](https://coldletter.com/blog/merge-tags/): A merge tag is a placeholder in your email template that your ESP replaces with recipient-specific data at the moment each message is sent. Write {{ customer.first_name }} once in your template, and every subscriber gets their actual name in that spot. The placeholder is gone by the time the email hits an inbox; what […]
- [Email Webhooks: Handling Bounces, Opens, and Delivery Events](https://coldletter.com/blog/email-webhook/): Email webhooks are HTTP POST requests your provider sends to your server each time something happens to a message: it gets delivered, bounced, opened, clicked, reported as spam, or unsubscribed. Rather than polling an API to find out what happened to a send, you register an endpoint once and the provider calls you. Every serious […]
- [How to Send HTML Email (the Right Way)](https://coldletter.com/blog/send-html-email/): Sending an HTML email the right way means setting both an HTML body and a plain-text alternative in a single message. Email clients receive a multipart/alternative structure and pick the richest version they can display. Clients that can show HTML render the styled version; others fall back to plain text. Skipping the text fallback is […]
- [Transactional vs Marketing Email: What's the Difference?](https://coldletter.com/blog/transactional-vs-marketing-email/): Transactional email and marketing email are not the same thing, and mixing them up causes real problems: broken compliance, damaged sender reputation, and password-reset emails buried under bulk-mail filters. Transactional emails are triggered by a specific action the recipient already took, such as placing an order or resetting a password. Marketing emails are sent to […]
- [Trigger Emails: Types and How to Send Them](https://coldletter.com/blog/trigger-email/): A practical guide to trigger emails: how they differ from broadcasts, the event-driven send model, common types (welcome, onboarding, transactional, dunning), and implementation patterns for SaaS teams.
- [Sender Reputation: What It Is and How to Protect It](https://coldletter.com/blog/sender-reputation/): Sender reputation is the collective trust score that mailbox providers assign to your sending domain and IP address. A strong reputation gets your messages into the inbox. A damaged one gets them filtered, deferred, or blocked before they arrive. Unlike a single authentication check, reputation accumulates over time based on complaint rates, bounce behavior, sending […]
- [Google Postmaster Tools: Setup and How to Read Your Data](https://coldletter.com/blog/google-postmaster-tools/): Set up Google Postmaster Tools, verify your sending domain, and learn what each v2 dashboard tells you about Gmail deliverability.
- [Email Design Best Practices for Developers and Marketers](https://coldletter.com/blog/email-design-best-practices/): Practical HTML email design guide covering layout, mobile-first responsive patterns, dark mode, accessibility, image-to-text ratio, and cross-client testing.
- [Postmark vs SendGrid: Transactional Email Compared (2026)](https://coldletter.com/blog/postmark-vs-sendgrid/): Postmark vs SendGrid compared side-by-side: pricing, deliverability, API quality, log retention, and marketing features. Practical guidance for SaaS teams choosing a transactional email service.
- [Best Postmark Alternatives for Developers (2026)](https://coldletter.com/blog/postmark-alternatives/): Postmark earns its reputation for transactional deliverability, but the per-email pricing adds up at volume, there is no native lifecycle automation, and the ActiveCampaign acquisition has introduced account management concerns for some teams. Here are the seven best alternatives organized by what you are actually trying to fix.
- [Best Amazon SES Alternatives for SaaS Teams (2026)](https://coldletter.com/blog/amazon-ses-alternatives/): Amazon SES is the cheapest email infrastructure at $0.10/1,000 emails, but teams hit a ceiling: no template UI, manual bounce handling, sandbox approval friction, and add-on deliverability monitoring. This comparison covers seven real alternatives with verified pricing and honest trade-offs.
- [Welcome Emails: Examples, Timing, and What to Send](https://coldletter.com/blog/welcome-email/): The welcome email is the single highest-performing message in your entire email program. According to GetResponse’s 2024 Email Marketing Benchmarks report, which analyzed 4.4 billion messages, welcome emails achieve an average open rate of 83.63% and a click-through rate of 16.60%, far above any campaign type they track. That window closes fast: subscriber attention is […]
- [Email Subject Lines That Get Opened: Patterns and Examples](https://coldletter.com/blog/email-subject-lines/): The subject line is the only part of your email that competes for attention before anyone opens it. If it fails, the rest of your work, the copy, the design, the personalized offer, goes unread. Getting it right is less about tricks and more about a short list of reliable patterns, applied with discipline. This […]
- [Email API: How to Send Email Programmatically (2026)](https://coldletter.com/blog/email-api/): Whether you need an email API or SMTP relay depends on what you want to do after a message leaves your application. If you only need to send, SMTP is fine. If you need delivery receipts, bounce handling, click tracking, and template rendering in one request, you want an HTTP email API. Most SaaS teams […]
- [Email Deliverability Best Practices: The Complete Guide (2026)](https://coldletter.com/blog/email-deliverability-best-practices/): Practical guide to email deliverability for SaaS teams: authentication, list hygiene, sender reputation, Gmail/Yahoo requirements, and monitoring.
- [SendGrid vs Mailgun: Which Should You Use? (2026)](https://coldletter.com/blog/sendgrid-vs-mailgun/): Pick SendGrid if your team needs built-in marketing automation alongside transactional email, or if you want a single platform that handles both API sends and campaign management. Pick Mailgun if you want a leaner developer-focused API, EU data residency without a plan upgrade, or built-in email validation without buying an add-on. Neither is universally better. […]
- [Best Mailgun Alternatives for Developers (2026)](https://coldletter.com/blog/mailgun-alternatives/): If you’re reconsidering Mailgun, the reason usually falls into one of three buckets: pricing increases after the Sinch acquisition, shared-IP deliverability that has measurably declined, or support that degrades at lower plan tiers. The best replacement depends on which of those is your primary pain point. For raw deliverability on transactional email, Postmark is the […]
- [Best Brevo Alternatives for SaaS Teams (2026)](https://coldletter.com/blog/brevo-alternatives/): The right Brevo alternative depends on what is driving you to look elsewhere. For pure transactional sending with top inbox placement, Postmark or Resend are the clearest upgrades. For SaaS lifecycle automation, Loops or Customer.io handle event-triggered workflows that Brevo handles inconsistently. For developer teams wanting a single platform that covers templating, automation, and API integration together, the options narrow further.
- [React Email: Build and Send Emails with React (Step-by-Step)](https://coldletter.com/blog/react-email/): The react-email library by Resend lets you write email templates as React components, preview them in a local browser, and render them to battle-tested HTML with a single render() call. No more wrangling hand-coded table layouts or context-switching to a MJML file: your templates live next to your app code, accept TypeScript props, and get […]
- [Soft Bounce vs Hard Bounce: What They Are and How to Handle Them](https://coldletter.com/blog/soft-bounce-vs-hard-bounce/): Understand the difference between soft and hard email bounces, the SMTP reply codes that signal each type, and the correct programmatic handling: retry soft bounces, suppress hard bounces immediately.
- [What Is Email Authentication? SPF, DKIM, and DMARC Explained](https://coldletter.com/blog/what-is-email-authentication/): SPF, DKIM, and DMARC are the three DNS records that determine whether a receiver trusts your email. Here is what each one does, what each one does NOT do, and how they work together to protect your domain and keep your mail out of spam.
- [What Is SMTP? How Email Sending Actually Works](https://coldletter.com/blog/what-is-smtp/): SMTP is the 40-year-old protocol behind every email you send. This guide explains the full journey from your app to the inbox, including the SMTP conversation, ports, relay services, and when a sending API beats SMTP.
- [Dunning Emails: How to Recover Failed Payments and Reduce Churn](https://coldletter.com/blog/dunning-emails/): A dunning email is an automated message sent to a subscriber after a payment fails, asking them to update their billing information or take action to recover the charge. For SaaS companies, these emails are the primary tool for fighting involuntary churn: the revenue lost not because customers chose to leave, but because a card […]
- [SaaS Onboarding Email Sequence: A Step-by-Step Framework (with Examples)](https://coldletter.com/blog/saas-onboarding-email-sequence/): A SaaS onboarding email sequence is a series of automated emails sent to new signups with one specific goal: get the user to their activation milestone, the moment they first experience the product’s core value. Not just “welcome them.” Not “show every feature.” Drive them to the aha moment that makes cancellation feel like a […]
- [Why Do My Emails Go to Spam? (And How to Fix It)](https://coldletter.com/blog/why-do-my-emails-go-to-spam/): Emails go to spam for five main reasons: missing or broken authentication (SPF, DKIM, DMARC), a damaged sender reputation (high spam complaints, too many bad addresses), low recipient engagement, spammy content or formatting, and an IP or domain that is on a blocklist. Fix authentication first, since it is the single highest-leverage change and the […]
- [Best Transactional Email Services Compared (2026)](https://coldletter.com/blog/best-transactional-email-services/): Quick verdict by use case: For highest deliverability with the least configuration, Postmark is the consistent recommendation. For low-cost high volume on an AWS stack, Amazon SES at $0.10/1,000 emails is hard to beat. For developer experience and React/Next.js teams, Resend stands out. For a combined transactional + marketing + automation platform, Brevo covers both […]
- [Best Mailchimp Alternatives for SaaS Teams (2026)](https://coldletter.com/blog/mailchimp-alternatives/): The right Mailchimp alternative depends on why you’re leaving and what you need next. For SaaS lifecycle and automation teams, Customer.io or Loops handle event-triggered onboarding and product-driven workflows that Mailchimp handles awkwardly. For creators and simple senders who want clean newsletters without contact-based price creep, MailerLite or Brevo are the most cost-effective replacements. For […]
- [Best SendGrid Alternatives for SaaS Teams (2026)](https://coldletter.com/blog/sendgrid-alternatives/): The right SendGrid alternative depends on what’s actually driving you to look elsewhere. If the issue is shared-IP deliverability, Postmark or Resend solve that with transactional-only infrastructure. If pricing at scale is the problem, Amazon SES undercuts everyone on raw cost but hands you all the operational complexity. If you need lifecycle automation alongside transactional […]
- [Email Automation for SaaS: Workflows That Drive Activation and Retention](https://coldletter.com/blog/email-automation-for-saas/): Email automation sends messages based on user behavior and lifecycle stage rather than fixed broadcast schedules. For SaaS, the five workflows that matter are onboarding, trial conversion, retention, expansion, and re-engagement.
- [How to Send Email in Node.js (Nodemailer, Step-by-Step)](https://coldletter.com/blog/how-to-send-email-in-nodejs/): Send email in Node.js with Nodemailer: install, configure SMTP, call sendMail(), verify connections, add attachments, and scale with a provider HTTP API.
- [How to Send Email in Python (Step-by-Step)](https://coldletter.com/blog/how-to-send-email-in-python/): The fastest way to send email in Python is with the standard library: smtplib + EmailMessage. Here is a minimal working example that connects to an SMTP server and sends a plain-text message: That covers the hello-world case. For production use, most teams send through a transactional email service rather than raw SMTP. The sections […]
- [How to Set Up DMARC (Step-by-Step Guide)](https://coldletter.com/blog/how-to-set-up-dmarc/): DMARC (Domain-based Message Authentication, Reporting & Conformance) tells receiving mail servers what to do when a message claims to be from your domain but fails SPF or DKIM checks. Setting it up takes about 15 minutes: you publish one DNS TXT record, collect reports for a few weeks, and then tighten the policy. Start here: […]
- [What Is Transactional Email? A Developer’s Guide](https://coldletter.com/blog/what-is-transactional-email/): A transactional email is an automated, one-to-one message sent to a specific user in direct response to an action they took or a system event that concerns them: a password reset, an order receipt, an account verification code, a shipping update. Unlike a marketing campaign that goes to a list, a transactional email is triggered […]
- [Cold Email + SaaS Marketing: A Growth Strategy That Actually Works](https://coldletter.com/blog/cold-email-vs-lifecycle-email-for-saas/): Cold email and lifecycle email marketing serve different jobs in a SaaS growth strategy — and most teams conflate them. Here is how to run both channels correctly, why deliverability is the deciding factor in cold outreach, and where Cold Letter fits in.
- [How SaaS Companies Use Cold Email to Drive Growth](https://coldletter.com/blog/cold-email-for-saas/): Cold email remains one of the highest-ROI outreach channels for SaaS teams — when built on the right infrastructure. Learn how to structure campaigns, authenticate your domain, and use Cold Letter to book meetings at scale.
- [Email Marketing Tools for SaaS: Building the Right Stack](https://coldletter.com/blog/saas-email-marketing-strategy-and-tools/): Most SaaS teams use the wrong tools for at least one email channel. This guide covers how to pick transactional APIs, lifecycle ESPs, and cold outreach tools at seed, growth, and scale — plus integration and stack decisions that matter.
- [SaaS Lifecycle Email Sequences: Trial Onboarding to Expansion](https://coldletter.com/blog/saas-lifecycle-email-sequences/): Most SaaS teams build one onboarding email and call it a lifecycle program. Here is how to build the four sequences that actually move users from trial to expansion: onboarding, feature adoption, win-back, and expansion.
- [Email Marketing for SaaS Growth: What Moves the Needle](https://coldletter.com/blog/email-marketing-for-saas-growth/): Email drives an ROI of $36 for every dollar spent, but only when SaaS teams treat it as three distinct channels, not one. This guide covers the lifecycle sequences, cold outreach tactics, and deliverability fundamentals that separate email programs that grow revenue from those that don’t.

## Pages

- [About](https://coldletter.com/about/)
- [Pricing](https://coldletter.com/pricing/): Pricing Pay for the craft, not the send. Coldletter prices on templates and journeys — your provider bills you for delivery. Start free, scale when you’re ready, and never get surprised by a per-email tax. Starter For a first integration and your transactional basics. $0/ forever Start free Up to 5k emails / month Up […]

## Optional

- [Agent (MCP protocol)](websites-agents.hostinger.com/coldletter.com/mcp)

[comment]: # (Generated by Hostinger Tools Plugin)