Hi, Thanks for the reply. We’ve also started seeing improvements here a few hours ago.
About 90% of the IPs that were having issues are now able to send messages. Best regards, Fernando M M On Fri, May 15, 2026 at 7:49 AM Areeb via mailop <[email protected]> wrote: > Lots of people and ESPs have had this issue over the last few days. > Apparently, Microsoft is aware of the problem and is working on a fix. > > We have started seeing improvements in deliverability today. > > [image: Regards,] > > Areeb Majeed > Co-founder, > Maileroo > > [image: icon] maileroo.com [image: icon] [email protected] > > [image: facebook] <https://facebook.com/maileroo> > > [image: linkedin] <https://www.linkedin.com/company/maileroo/> > > [image: twitter] <https://twitter.com/maileroodotcom> > > [image: __tpx__] > > *Maileroo Group Pty Ltd |* Level 10, 440 Collins Street, Melbourne VIC > 3000 > > On 15/05/2026 8:01:03 PM, [email protected] < > [email protected]> wrote: > Send mailop mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > https://list.mailop.org/listinfo/mailop > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of mailop digest..." > > > Today's Topics: > > 1. Persistent Outlook.com S775 rate limiting since May 8? > (Fernando MM) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Thu, 14 May 2026 22:57:02 -0300 > From: Fernando MM > To: Mailop > Subject: [mailop] Persistent Outlook.com S775 rate limiting since May > 8? > Message-ID: > > Content-Type: text/plain; charset="utf-8" > > Hi all, > > We’re trying to determine whether others are experiencing similar > Outlook.com delivery issues that started around May 8. > > Multiple IPs suddenly began receiving the following error: “451 4.7.650 > The > mail server [IP] has been temporarily rate limited due to IP reputation > (S775).” > > The issue appears to be persistent. Retrying after 12, 24, or even 48 > hours > has no effect, and no messages can be delivered from the affected IPs. > > We also opened tickets through https://olcsupport.office.com/. Support > consistently replies with messages similar to: > > * “We have implemented mitigation for your IP (XXX), and this process may > take 24–48 hours to replicate completely throughout our system.” > * “Please try sending emails again within the next 12 hours and let us > know > if you continue to experience issues.” > > However, after waiting the requested time, the exact same error continues. > When we follow up, we receive essentially the same response again, which > leaves us stuck in a repeating support loop. > > Is anyone else seeing similar persistent S775 reputation throttling issues > since May 8, particularly in cases where mitigation was reportedly applied > but had no visible effect? > > Thanks, > > Fernando M M > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > mailop mailing list > [email protected] > https://list.mailop.org/listinfo/mailop > > > ------------------------------ > > End of mailop Digest, Vol 70, Issue 21 > ************************************** > > [image: 9b8094b8-dedf-4d84-bda9-d48269055674] > _______________________________________________ > mailop mailing list > [email protected] > https://list.mailop.org/listinfo/mailop >
_______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
