SMTP Errors

Decode and fix SMTP error codes (421, 450, 550, 554 and more) that prevent your emails from being sent.

3 articles

Cannot Connect to Mail Server? 7 Steps to Fix It

A 'cannot connect to mail server' error stops your email client from sending or receiving. This step-by-step guide covers every common cause — wrong settings, blocked ports, SSL issues — and how to fix each one.

Beginner 3 min read 3 May 17

How to Fix SMTP Error 550: Email Rejected Explained

SMTP error 550 means your email was permanently rejected. Learn the most common causes — wrong address, blacklisted IP, missing SPF — and fix them step by step.

Intermediate 3 min read 3 May 17

SMTP Error Codes Explained: Causes and Fixes

Decode the most common SMTP error codes (421, 450, 550, 554, and more). Understand what each code means and how to fix it quickly.

Intermediate 3 min read 4 May 17