Exchange ActiveSync Sent e-mails not syncing correctly in Apple Mail on iPhone
We are using Exchange 2016 on our e-mail server and I am using ActiveSync in Apple Mail app to sync my e-mails to my iPhone 14. My inbox and sent items do indeed transfer to my iPhone. The problem I am having is that often when I search for an e-mail that I've sent (can be newer or older) from Outlook on my Windows PC, I cannot find it under sent e-mails on my iPhone, even though seemingly all of the other sent e-mails have synced just fine. Even if I go look for it manually, by scrolling and not using search bar, I don't have it. But, every time after about 5 minutes of me searching for the email, it then appears, so it appears to be a syncing issue.
I have tried resetting the phone, removed and re-added the account in question, and a bunch of other things. I want to use the ActiveSync feature so my e-mails get pushed when they arrive. The sent e-mails sync just fine on other devices.
What could be the issue? I would appreciate any help with this. Thank you.
iPhone 14