Unable to add email alias which was working before

Question

Hello, I am trying to add secondary email alias for one of our internal users but it's throwing the below message in all places (Exchange PowerShell, Exchange GUI, and in O365); This used to work before but I have no idea what could have caused the issue. Any help would be much appreciated. We don't have on-prem Exchange.

Thank you.

Answer 1

Are you syncing from on-prem to Azure? Its not a hybrid issue as much as the syncing from on-prem that causes that error

Answer 2

@Shamyog

For sync AD account, you need to modify from the local AD (ADUC). Many of attributes cannot modified from the Exchange online side.

For emails address, you need to modify the "proxyAddresses" value from the ADUC. Such as "smtp: User@keyman .com". Then wait the sync of AAD Connect.

If there doesn't exist Exchange on-premises server, I would suggest you run prepare command with Exchange server ISO on your local AD. Otherwise, you cannot see the mail related attributes and modify from the local AD.

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