How I can add mail alias (second address) for O365 account that has been synced with the local AD system?

Question

I have one account in my local AD which has been synced with Azure AD cloud.
I need to add another (alias) email to it's account but got the error in ExO:

"Error executing request. An Azure Active Directory call was made to keep object in sync between Azure Active Directory and Exchange Online. However, it failed. Detailed error message: Exception happened when doing AAD dual-write.'

I have no Exchange in my local AD.

How I can add additional email addresses to synced accounts like that?

Answer 1

Hi @Allan Stark ,

go to AD User and Computer, find the user, doubleclick -> attribute editor -> find "proxyAddresses".
add the address

NOTE:
if there are no values at all in the attribute, please add the value like this:
SMPT:primaryEmail@yourdomain.com
smpt:emailyouwanttoadd@yourdomain.com

every further email needs to be added with "smtp:thenyourmail@yourdomain.com"

as Andy already said - this is not supported from Microsoft. But it works very well ;-)

Answer 2

Add to the on-prem object via ADUC or ADSIEDIT and it will sync via AADConnect within 30 minutes.

Note its not supported to have AADConnect syncing to 365 and not have at least one Exchange Server on-prem for mgmt.

Answer 3

And after synchronization I need to set primary (reply) address in ExO?

no, this is done by SMTP: and smtp:
SMTP: is primary
smtp: is secondary

Answer 4

Thank you for your answer.
I need to add both addresses (main and alias) to the proxyAddress field of the user object, right?
And after synchronization I need to set primary (reply) address in ExO?

Answer 5

Thank you! All works well!