The Coldletter blog
Category: Blog
Articles about transactional and marketing emails.
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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…
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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…
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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…
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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.
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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…
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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.
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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.
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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.
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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.
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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.
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Welcome Emails: Examples, Timing, and What to Send
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…
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Email Subject Lines That Get Opened: Patterns and Examples
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…