Possible Causes for Mobile Users' Inability to Connect to Microsoft Exchange 2016 on Premises
Question
Almost all users receive their emails on their mobile devices, but some users are not able to connect to Microsoft Exchange 2016 while on premises.
What can cause this issue?
Answers
Explanations
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A. B. C. D.A.
The issue described in the question is that some users are unable to connect to Microsoft Exchange 2016 while on premises, while almost all other users can access their emails on their mobile devices. This suggests that there is a specific problem affecting a subset of users, rather than a general issue with the Exchange server or email system as a whole.
Option A, which suggests that the affected users may be Workspace ONE UEM Console administrators who require additional permissions on the Exchange server, is unlikely to be the cause of the issue. While it is possible that certain users may require additional permissions to access Exchange, it is unlikely that this would affect only a subset of users while leaving others unaffected.
Option B, which suggests that the affected users may be members of the Exchange Organization admin group, is also unlikely to be the cause of the issue. While membership in this group can provide additional access to Exchange resources, it is unlikely that this would prevent some users from connecting to Exchange while allowing others to do so.
Option C suggests that the Apple Push Notification (APNS) certificate may be expired and needs to be updated. This is a more likely cause of the issue, as an expired APNS certificate can prevent mobile devices from receiving push notifications, which are used to alert users of new emails and other events. If the affected users are unable to receive push notifications, they may not be able to access their emails on their mobile devices. Updating the APNS certificate should resolve this issue.
Option D suggests that secure email gateway (SEG) services may not be running and that the SEG server may not be a member of the Active Directory. While this could potentially cause issues with email delivery or access, it is unlikely to be the cause of the specific issue described in the question, which involves some users being unable to connect to Exchange while on premises.
In summary, the most likely cause of the issue described in the question is an expired APNS certificate. Updating this certificate should resolve the issue and allow affected users to access their emails on their mobile devices.
