iOS 18.3.1 and email sync issues

[robberthiaume]

I have a location that iOS devices on 18.3.1 are having issues syncing email with O365.  It is only affecting those devices that are at iOS18.3.1.  Has anyone else experienced this?

[RaphaelL]

Hi ,

Are you using a MX ? Any content filtering applied ?

[robberthiaume]

I am not using an MX, I have a Fortinet 81F firewall. All the devices running any iOS other than the 18.3.1 are working fine. just the iPhones and iPads running 18.3.1 are affected, and it is only affecting the email sync with O365, all other traffic is working fine.

[PhilipDAth]

Does the firewall show anything being blocked when you go to do a sync?

I assume you are using Outlook for iOS?  Please don't use Apple Mail.

[jwest512]

We've seen one user so far (perhaps others haven't noticed yet) with O365 sync issues using the native/apple mail client since updating to iOS 18.3.1. I'm quite certain it's an apple bug. We're Palo Alto firewalls and I show zero blocked traffic/url/threat from that source IP in our logs. 

Yes using the Outlook app would be ideal and i'm sure Microsoft would prefer, but that's not something we can force on users yet.

I'll reply back here if we make any progress. Lots of other rumblings on the internet about this issue.

[PhilipDAth]

I have had lots of issues with users and Apple Mail.  It is now a configuration we refuse to support.  Use Outlook for iOS or resolve the problem yourself.  We take a hard line on it now.  Apple Mail has wasted too much time.

Outlook for iOS also adds in many other features (like OneDrive and Sharepoint for file access) that users of Apple Mail miss out on.

[robberthiaume · Accepted solution]

I worked with our onsite tech person yesterday afternoon and did an uninstall/reinstall of the mail app, then a Force restart of the device.  This cleared the issue on the iphones and ipads  that were having email sync issues while running iOS 18.3.1.  Give this a try and let me know if this resolves the issue for you as well.