The Coldletter blog

Category: Blog

Articles about transactional and marketing emails.

  • Re-Engagement Emails: How to Win Back Inactive Users

    Re-Engagement Emails: How to Win Back Inactive Users

    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

    Merge Tags and Dynamic Email Content Explained

    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

    Email Webhooks: Handling Bounces, Opens, and Delivery Events

    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)

    How to Send HTML Email (the Right Way)

    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?

    Transactional vs Marketing Email: What’s the Difference?

    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

    Trigger Emails: Types and How to Send Them

    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

    Sender Reputation: What It Is and How to Protect It

    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

    Google Postmaster Tools: Setup and How to Read Your Data

    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

    Email Design Best Practices for Developers and Marketers

    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)

    Postmark vs SendGrid: Transactional Email Compared (2026)

    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)

    Best Postmark Alternatives for Developers (2026)

    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)

    Best Amazon SES Alternatives for SaaS Teams (2026)

    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.