We have used the Bulk Email tool for a while sending large email blasts (at least for us) of 200 emails to 250 emails.  Withink the last two weeks we have started to get email messages from O365 warning of account compromise - High Severity.

Our Managed IT provider is telling me this is baked in to O365, but we have never received until two weeks ago.  Does anyone else have this issue or know of a fix?