Don’t use “Outlook (new)” in #Windows 11. I just did a tcpdump and looked also at my #mail servers when setting up an account in there. The mail client only spoke with Microsoft-servers, never with my mail-servers and I saw on my mail-servers only connections from Microsoft-IPs.
@nielsk So would it make sense to block MS on submission and IMAP ports? What legitimate business could they have?
@unixtippse If your users use the new Outlook which will replace Windows Mail you can’t block them.
@nielsk @unixtippse I think from a security point of view, it's better when it doesn't work. More than that, every time your server sees a user successfully log in from a Microsoft IP, it should reset (or disable) that user's password, since you have to assume it's compromised.