Exchange Send As permissions are not applying

Problem: Send As permissions are not setting in the panel

Reason 1: If the user's CName (CN) in Active Directory is not in proper format i.e. as shown in the below screenshot, then this issue happens.

This usually happens, if the mailbox is created manually from ECP.

Resolution: To resolve this issue, please modify the CName of the user in a proper format in Active Directory by renaming it as shown in the below screenshot:

After performing the above step Trigger Sync the organization in the HC panel. For Trigger Sync please refer to the below article:

Reason 2:
If the Owner of the AD object is different from the user configured in Exchange Server role in HC at Configurations >> Servers >> Edit Exchange Server. Normally this case appears if you have created the user manually in the Active Directory and later you enable mail services.

To see the owner of the AD object, open Active Directory by clicking Start >> run >> dsa.msc and then navigate to Organizational Unit > Select Account >> Properties >> Security >> Advanced. For further clarity see the screen below:

Resolution : To resolve the issue, you must modify the owner to reflect the same user that is configured in HC Exchange Role Configurations.