Configure Exchange Online SMTP Relay with a Static Public IP Address

This article provides a step-by-step guide on configuring an Exchange Online SMTP relay using a static public IP address, as Microsoft deprecates Basic Authentication for SMTP AUTH. It covers prerequisites such as Exchange Online licensing, a static public IPv4 address, port 25 TCP access, DNS SPF configuration, and required admin roles. The guide explains how to create an Exchange Online connector for SMTP relay, determine the MX endpoint, and set up SMTP settings for devices and applications. It also includes PowerShell testing commands and solutions for common issues like relay denied, tenant not authorized, connection errors, and messages marked as spam. This is a technical tutorial for IT professionals managing email relay for legacy devices.