More-reliable email in WordPress 6.9

Emails sent from WordPress will be more reliable in WordPress 6.9 thanks to a few updates and bug-fixes to the wp_mail() function.

The sender address is extensibly configured.

The sender address, also known as the Envelope-From, the MAIL FROM, the Return-Path (and even more), is the address where other email servers send “bounce messages” when they can’t deliver a message. Since WordPress 4.7.0 this value was being set by the outgoing mail server and would often end up misconfigured^{1. That doesn’t sound like it should be a big problem — a site may not receive those notifications from}