I have a few users whose emails are being blocked from sending.

Copper Contributor

We notice that this only occurs within one domain. M365 are blocking users from sending out emails within the organization. We check to enure that our tenant has not been compromised. This strangely happens randomly, and the policy is in its default settings. I read around the community and was unable to find a resolution. When will MS fix this issue ?


Error message :
"Suspicious messages in last 24 hours: 396 Total outbound messages in last 24 hours: 1;Percentage of suspicious messages: 39.600%;Last Message ID: 918c961f-9ef9-4658-f70e-08d988e704da"

1 Reply


Likely the number of outgoing messages and maybe their content is getting them flagged as spammers.

If these are users that are mass emailing, then maybe signing up for a service that specialized in that might be appropriate as Microsoft's servers aren't intended for mass emails.