Email testing, deliverability, and API guides

Build more reliable email and SMS workflows with practical MailSlurp tutorials, implementation guides, and production-ready testing advice.

Top 3 Email Testing Tools in 2026 (And How to Choose the Right Stack)

Mar 2, 20263 min read

Compare top email testing tools for automation, rendering, and deliverability. Use this shortlist to choose a stack that fits your release risk.

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Deliverability

SpamAssassin spam filters: setup, testing, and tuning playbook

Mar 2, 20263 min read

Set up SpamAssassin spam filters, run SpamAssassin tests, tune rule thresholds, and operate production mail filtering safely.

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Email testing

SMTP4dev Guide: Local Email Testing, Limits, and CI Strategy

Mar 2, 20263 min read

Use smtp4dev for local email testing, inspect outbound messages safely, and understand where local fake SMTP should be replaced by cloud test workflows.

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Email testing

SMTP Relay Testing Guide: Open Relay Checks, Auth Validation, and Inbox Proof

Mar 2, 20267 min read

Test SMTP relay behavior safely with open relay checks, authenticated sends, inbox receipt, header review, webhook evidence, and CI assertions.

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SPMailSlurp field guideEmail testing

SMTP Port Guide: 25 vs 465 vs 587 vs 2525

Mar 2, 20263 min read

Understand SMTP ports 25, 465, 587, and 2525, when to use each, and how to validate connection, auth, and delivery behavior before release.

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Email testing

SMTP Commands and Response Codes (Practical Reference)

Mar 2, 20263 min read

Use this SMTP commands and response codes reference to debug authentication, TLS, recipient, and delivery issues in production email workflows.

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PAMailSlurp field guideSMTP & APIs

Plus Addressing for Customer-Level Email Routing

Mar 2, 20263 min read

Implement email plus addressing to route customer replies and inbound messages into deterministic webhooks, queues, and support workflows.

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Email testing

Nodemailer NPM Guide: Send Email with Node.js and Test Delivery

Mar 2, 20267 min read

Install Nodemailer from npm, configure Node.js SMTP, fix common send errors, and test real inbox delivery with MailSlurp.

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NMMailSlurp field guideEmail design

NBSP Meaning in HTML Emails and Why It Matters

Mar 2, 20264 min read

Learn the nbsp meaning, how the non-breaking space character works in HTML emails, and when to use it safely in templates.

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Email testing

Mailinator Alternatives: Private Inboxes, APIs, and CI Testing

Mar 2, 20263 min read

Compare Mailinator alternatives for private inbox testing, API automation, and CI reliability. See when to move beyond public Mailinator email workflows.

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Email testing

MailHog Tutorial: Docker SMTP Capture, mhsendmail, and CI Email Testing

Mar 2, 20264 min read

Set up MailHog with Docker, capture local SMTP messages, test mhsendmail, and move release checks into MailSlurp inbox assertions.

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MIMailSlurp field guideEmail testing

MailCatcher Introduction: Local Email Debugging and Migration Path

Mar 2, 20263 min read

Learn what MailCatcher does, where it helps in local testing, its limitations, and how to move to shared CI-ready email testing workflows.

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