Office 365 Exchange Online server blacklisted

Steel Contributor

At 10:20AM 24 Nov AEST I'm seeing reports that Office 365 Exchange Online server is appearing on different blacklist sources


I've raised a support ticket but thought I'd post in here in case anyone else is impacted.


It's preventing one of our clients emailing payslips to staff who have etc addresses or any personal address being protected by blacklist checks.


Will update this when Microsoft have resolved.



9 Replies

Hi Sonia,


Maybe same issue as my customers have:


I see a lot of emails are send through the high risk delivery pool and yes this pool is on some blacklists, but the regular pool is not.


I spoke to a MS engineer yesterday, the see the last days more of this issues at customers, it is already escaleted to the team who is responsible for this.





This is where being an Exchange admin gets frustrating. On our own servers, we'd investigate, remediate and apply for the listing to be removed. With Exchange Online, Microsoft will do the same  ... eventually. It just takes them longer.


On the upside I never need eseutil.


So we wait.



Microsoft confirmed the issue is resolved.
I don`t see messages send through the high risk delivery pool anymore.




Peter is still reporting that Exchange Online server as being blacklisted on 6 different services.

Ok, but the issue was all email send to Hotmail, Gmail etc was send via the High Risk Delivery Pool and that issue was solved. Yes this pool of servers is still on the blacklist, but this is not the server pool which is used to send. Have a look at this article for more information about the server pool:

I see, thanks for the link Peter, that was helpful.

I've been called today to say the Microsoft have fixed our issue which was impacting about 20 customers. I'm just about to retest it.



@Peter Klapwijk Are you seeing this again? We had a different client contact us today with a non-suspicious email that had been blocked via the blacklisted high risk server again.

Hi @Sonia Cuff No, none of our customers reported a problem like this since this one was resolved.

OK, thanks. I'll get her to retry in the morning and will log a new call with support if we need to.