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MailSlurp resources

Guides

Practical guides for MailSlurp messaging, testing, reliability, extract, account setup, and procurement workflows.

Use this hub when you know the workflow you need to ship but want the fastest implementation path. The highest-demand guide topics in our product set map to messaging setup, email and auth testing, sender reliability, and inbound extraction, so this page is organized around those jobs instead of a flat documentation list.

Messaging guides

Use these guides when you need inboxes, domains, routing, or message-event integration:

Testing guides

Use these guides when your release process needs message proof, device previews, or auth-flow validation:

Reliability guides

Use these guides when sender posture, open tracking, or delivery confidence needs a clearer operating model:

Extract and automation guides

Use these guides when inbound messages or attachments need to become structured downstream work:

Developer quickstarts and examples

Account, support, and procurement

More in this section

550 Permanent Failure Blocked: What It Means for One or More Recipients and How To Fix ItLearn what `550 permanent failure blocked` and `550 permanent failure for one or more recipients` usually mean, which recipient and policy problems trigger them, and how to fix the message path without guesswork.A/B Email Testing: Practical Experiment Design For Better ConversionsLearn how to design valid A/B email tests, choose the right metrics, avoid false winners, and roll out improvements safely.Alias Email Address Proxy: Forwarding, Masking, and Routing WorkflowsLearn how alias email address proxy workflows handle forwarding, masking, and routing, and how teams use them for support, testing, and inbound automation.All you should know about SPF email recordsVerify your email security and prevent email spoofing with SPF. Learn how it works and create your SPF record to protect your reputation.Automated Email Replies with Inbox Repliers PlusConfiguring Automated Email Reply Rules for Inboxes and Catch-All Addresses using MailSlurp. Set up customizable repliers, track events, and more!Avoid email bounces and improve reputation by following best practicesSetup bounce notification webhooks for your account to reduce email bounces. Respond to bounce events by saving bounce recipients.Avoiding email spam filtersMaster the art of email deliverability! Discover how to avoid spam filters and ensure your messages reach your audience with these expert tips.Batching API Requests for Email RecipientsSending emails with multiple recipients? Learn how to bypass MailSlurp's limits with batching in our guide on sending API requests.BCC and CC in SMTP Emails: API Fields, Headers, and TestsUnderstand CC and BCC in SMTP email, how recipient fields behave in APIs, and how to test BCC visibility with MailSlurp inboxes.BCC in Email: Meaning, Examples, and When to Use ItLearn BCC meaning in email, what BCC does, when to use BCC vs CC, Outlook BCC behavior, and how to test recipient privacy with MailSlurp.Best SMTP Port: 25 vs 465 vs 587 vs 2525Compare SMTP ports 25, 465, 587, and 2525. Learn which SMTP port to use for app sending, relay, STARTTLS, implicit TLS, and MailSlurp validation.C# email tutorial for SMTP sending and inbox testingSend and receive email in C# with MailKit and MailSlurp. Practical .NET patterns for SMTP setup, inbox waits, attachments, and verification flows.