The Coldletter blog
Category: Blog
Articles about transactional and marketing emails.
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How to Build a Responsive HTML 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.
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What Is BIMI? Brand Logos in the Inbox Explained
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…
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Double Opt-In: What It Is and Why It Protects Deliverability
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.
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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.
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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…
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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.