Blog Post

Microsoft Defender for Office 365 Blog
5 MIN READ

Strengthening Email Ecosystem: Outlook’s New Requirements for High‐Volume Senders

Puneeth's avatar
Puneeth
Icon for Microsoft rankMicrosoft
Apr 02, 2025

This applies to Outlook.com - our consumer service, which is supporting hotmail.com live.com and outlook.com consumer domain addresses.

April 29th Update - Changes have been made to the action take on messages that do not meet requirements, please see details below. Introduction In an era where email remains one of the most widel...
Updated Apr 30, 2025
Version 4.0
awareness & training
email protection basics
rhuxster's avatar
rhuxster
Copper Contributor
Jun 24, 2025

@#$%^&*

Undo whatever you did !

Can't send any email with attachments to Hotmail accounts. Gmail and other accounts okay.

Fix is way too technical, If the fix would even work as I am NOT using Outlook, I am using Yahoo yet I get this error for Outlook.

Microsoft fix whatever you did. It worked fine before, Put back what was.

pissed off!