Hello Md Nasir Uddin,
According to your description, in order to better understand and solve the problem, I would like to confirm the following issues:
- Could "Before one month" be understood to mean that one month ago was normal, or does it mean something else?
- When you mentioned "no mail is not showing" what do you mean?
- What client are you using now? Outlook for Android or the mail app that comes with Android? Is there the problem with both?
- whether this problem occurs in a single user or multiple users?
Please log in to OWA and see if everything is working there.
Besides, if the problem occurs with just one user, it is recommended that you reconfigure the account. Try deleting and re-adding your account to see if it works. If the issue is affecting all users, run Exchange Remote Connection Analyzer to test ActiveSync and see if it has any errors.
If there is any misunderstanding, please correct me.
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