Hi, I administer and moderate a library and information science professional list. The list is running on Mailman 2.1.26. There are nearly 5k list subscribers, of which almost 4k are 'digest' registrants. The majority of the registrations are with personal email IDs.
During the last couple of weeks, approved messages are not being delivered to the list members. When I check the Email & collaboration alerts in the Microsoft 365 Admin Portal, I see the following message:
Suspicious email sending patterns detected, User was restricted from sending emails.
Additionally, a pop-up on the screen reads:
"Unblock entities which have been blocked for sending too many messages marked as spam/bulk."
The first approved message gets delivered after unblocking the relevant email ID and approving another message after 24 hours. For the subsequent one, the emails bounced back, and the MS admin portal reported the same error messages mentioned above.
Can someone please help me fix this issue?
Thank you for your attention and time, Francis