We have Hybrid environment configured a few weeks ago. Started migrating users from on-Prem to O365.
Everything was working ok for the last two weeks. This morning cloud (O365) users started complaining that they receive Winmail.dat file attachments from On-premises users. Nothing that we changed on our end. When on-prem users send email to O365 user, winmail.dat file is getting attached. Our users have formatted signature in the body of the email.
According to some articles, the recommendation is to set MailFlow\RemoteDomains\Default\Use Rich text format to NEVER.
After making this change and waiting for a couple of hours basically nothing changed.