We have several executives using iphones that were recently migrated to Office 365. When their email was still on-prem, they had no problems with syncing their email. Sending, receiving, calendaring... It all worked fine.
Since they were migrated, they've all seen a very annoying behavior. Whenever they reply or reply-to-all when responding to an email on their phone, a copy of the message they just sent shows up in their inbox.
If they reply or reply-to-all using their PC, those emails don't show up in their inbox on the iphone. It only happens when the reply is done on the iphone itself.
I checked all the settings on their phones, and the only thing i could find was an option to BCC themselves on all messages. None of them had this enabled though.
This only seems to happen on iphones. We mostly use Windows phones, and nobody with one is effected.
None of them had any rules setup in Outlook.
I don't know the specific model or iOS version they have, but they all bought them new within the last month or two, so i'm assuming they're the latest and greatest.
I know next to nothing about iphones, so forgive my ignorance.
Any help is greatly appreciated.
(*Quick update. One of the users reports that they're seeing their own address in the CC field. Explains why they're getting copies of emails they're sending, but not how the address is being added to the CC.)