Hi,
To start, yes the "CC Myself" feature is not enabled on any of these devices. Any new iOS/EAS device the user is setup on exhibits this behavior. On emails sent only to him, the "reply all" feature is there unlike other user accounts where only "reply" available on direct email messages. It's like it doesn't recognize his address as belonging to the account. This is the only account in the org of nearly 2000 user accounts that behaves like this.
This account does have an unusual history. Our typical naming convention for accounts is {first initial}{last name}: jsmith. When a mailbox is created, its alias would be jsmith and its primary address would be jsmith@domain.com, which matches the UPN, with a john.smith@domain.com secondary. A couple years ago, this user wanted another initial added to his primary and to no longer receive mail at his previous primary and secondary. He was given jdsmith@domain.com while jsmith and john.smith were deleted. This is the only difference I know of between this account and any other account. On other accounts, we have varying primaries of first.last@domain.com and even name@otherdomain.com, and they all function perfectly fine. The only mitigating factor is they never had the email address that matched their UPN and alias base deleted. That said, I can't replicate this behavior by creating a test account and then editing it to match this. Do an autodiscover request returns valid results as well.
What else could be wrong with this account? Unfortunately this is an executive, so I'd like to avoid deleting the mailbox and recreating it given the unforseen issues that may cause. Likewise I've gone through multiple rounds of device testing, test accounts, etc, and I'm essentially at a place where I'm just throwing stuff against a wall to see what sticks. Thanks!
