Microsoft/Outlook has been rejecting all the mail from my mailing list server with this message. It says temporary, but it's been going on long enough that messages are timing out and bouncing, quite possibly a month or more, but I don't have enough MS subscribers that anyone complained until recently.
It's a tiny little server, it's been around for many years, and it's very unlikely to be sending mail that users object to. 2026-05-22 12:27:31.262250500 delivery 551907: deferral: Connected to 52.101.40.28 but sender was rejected./Remote host said: 451 4.7.650 The mail server [192.55.226.75] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postmaster (S775) [Name=Protocol Filter Agent][AGT=PFA][MxId=11BD6DD8C0C7A716] [CY4PEPF0000E9CF.namprd03.prod.outlook.com 2026-05-22T16:27:31.233Z 08DEB6EC620C7362]/ I tried to add my network 192.55.226.0/24 to SNDS, but it wants to send the confirmation mail to [email protected] because their WHOIS lookup is broken, too I renumbered my server a year or so ago and I suppose it's possible they've been grumpy since then, but other IPs in the same range that send to MS don't have that problem. R's, John _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
