#SMTP configuration

Tagged: SMTP configuration

07 Jul 2026Sam wallness

SMTP Authentication Errors: How to Diagnose and Fix AUTH Failures

SMTP authentication failures stop outgoing email cold. Whether you're seeing a 535 invalid credentials error, a 530 STARTTLS requirement, or a 454 temporary failure, this guide covers what each error means and exactly how to fix it.

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SMTP Server Hardening: A Practical Checklist for Securing Your Mail Server

SMTP & Infrastructure

07 Jul 2026Sam wallness

SMTP Server Hardening: A Practical Checklist for Securing Your Mail Server

A mail server connected to the internet is a high-value target for open relay abuse, spam injection, and phishing attacks. This checklist covers SMTP hardening essentials — from closing open relays and enforcing TLS to rate limiting, authentication records, and monitoring.

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