RE: mailbox features after migration

Hi IQA,

I fully understand your situation. The permissions and some features cannot be migrated from on-premises server to Office 365, you need to disable POP/IMAP feature after migration.
To disable POP/IMAP for the mailboxes by using the PowerShell cmdlets is a better way at present.

Given this situation, I suggest you submit feedback to Microsoft, including your comments or suggestions. The related group will deal with the feedback. The useful ideas and feedback will help us improve our products and service.

Thanks,
Edward Qu