Hi @Ahmed Gamal ,
When the type of the email account is Exchange, it's by design that the data will remain and sync with the Exchange server. Only POP protocal is designed for offline message processing and the downloaded messages are stored only on the local computer or device.
we have been using POP3....right now we are moving to exchange
By this, do you mean you are moving from another email system to Exchange?
If this describes your situation, actually it's supported to configure an Exchange user mailbox by using POP3 in Outlook as well, so you can consider keeping using POP3 propocal when adding the account. For more details about configuring POP3 on Exchange, you may refer to: Configure POP3.
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