Does ActiveSync store emails locally on iOS?

Thank you KiltedTim. Do you have any documentation that supports the case that the emails are cached locally on the device?

I do agree to some extent that the ActiveSync data potentially could be cached on a mobile device. There is a line that reads from Microsoft docs: "Exchange ActiveSync lets mobile phone users access their email, calendar, contacts, and tasks, and lets them continue to access this information when they're working OFFLINE." (https://docs.microsoft.com/en-us/exchange/clients/exchange-activesync/exchange-activesync?view=exchserver-2019) Offline, I suppose, means the mail contents must be cached on the local device. But when I spoke to an Apple techs, as suggested by LawrenceFinch above, they themselves did not know whether ActiveSync was cached locally on their own devices using their own operating system. After multiple Tier Supports, the best answer I got was that POP stores mails locally while IMAP does not. Technically, ActiveSync is neither one of those protocols. And again, it's not what the protocols do or don't do that I'm after. It's what the iOS device does with that content is what I'm after.

Problem is for regulatory purposes, I'm seeking out for a hard coded documentation that reads that "ActiveSync does or does not store mail locally on the iOS devices". And thus far, there appears to be zero findings on this. Apple support recommended I chase this on the Microsoft side of things. But as noted above, how ActiveSync functions is not the point of the matter here. Even if the assumption that it is simply a synchronization protocol to view/access online mailboxes, what I need to know from Apple is what they do with that data that syncs and is made available to mobile users even in an offline state.

Yes, company policies are definitely an integral part of determining actions to take in the event of terminations. Thank you for your suggestion on that. But policies may be different per company depending on different needs (company that allows personal devices that can't be wiped, company policies that prohibit BYOD but employees abusing the enabled activesync service, etc). My intent is not to go off topic and try and find some forms of plan Bs & Cs to different scenarios of terminations. I'm hoping this post will remain consistent with simply finding out whether iOS devices store ActiveSync locally even after disabling user account & ActiveSync.

In any case, this is not a rant. I wrote out the thought process to see if this discussion helps anyone in the future carry on with the investigation. Thank you again for your response.

Thank you for that. I guess I'll just have to keep digging.