Our ticket initially said "There are no issues with your IPs preventing email from reaching Outlook services." and when I replied with more information - it's been quite a while without a response.
That said from running a simple Google search for Microsoft 451 - it seems this is affecting an absolute metric ton of senders. Everything from universities to small businesses to big senders like SendGrid and the like. I've seen MXRoute in this thread as well - and they're monumentally bigger than we are [we only send 1,500 to 2,000 messages to Outlook every day]. I suspect their support staff are probably overwhelmed with tickets. I don't think there's anything I can do personally but sit back and wait for them to respond and monitor/watch this list. I do genuinely wonder the motivation for this and why it appears to have been so poorly implemented. If their goal was to set rate limits - with the data they have access to - it should have been trivial for them to set realistic default rate-limits even if it's per-IP. But alas - here we all are dealing with this. I know some of you are affected way more than we are and I hope Microsoft gets this figured out. Thank you, Michael Denney MDDHosting LLC http://www.mddhosting.com/ > On Feb 25, 2026, at 12:19 PM, John Quaglieri via mailop <[email protected]> > wrote: > > It is encouraging to see some senders getting a reset. I see a large number > of complaints on the learn.microsoft.com Q&A board for the same (S775) error. > Ticket responses I’m seeing are ranging at least 24 hours per response on my > own ticket which the last one was nothing is preventing these emails from > reaching. For now, I have slowed down mail going to Hotmail/Outlook domains. > > On 2/25/2026 11:50 AM, Jarland Donnell via mailop wrote: >> I would appreciate the same. At this point we're looking at severe options >> to react to this. I'm interpreting it as anti-competitive behavior aiming to >> destroy other ESPs at this point. I've gone round and round with their team >> via tickets and they genuinely just do not give a shit. >> >> On 2026-02-25 03:26, Matthew Francis via mailop wrote: >>> Frido Otten via mailop wrote on 2026-02-25 08:12: >>>> From my experience, some of them are lurking here as I do get direct >>>> messages sometimes asking for more information on an issue posted here. >>> >>> If that's the case, I'd appreciate a direct message from an MS lurker. All >>> of my MTA's are currently rate limited and I have not had a response to my >>> open ticket (7098423866). >>> >>> Thanks, >>> >>> Matt. >>> _______________________________________________ >>> mailop mailing list >>> [email protected] >>> https://list.mailop.org/listinfo/mailop >> _______________________________________________ >> mailop mailing list >> [email protected] >> https://list.mailop.org/listinfo/mailop > > -- > John Quaglieri > > _______________________________________________ > mailop mailing list > [email protected] > https://list.mailop.org/listinfo/mailop
_______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
