Ad connect : proxy address property not synching

[Marvin Oco]

We are setting the mail alias property from local AD proxy address property:

SMTP:user@contoso.com
smtp:user@contoso.onmicrosoft.com

Issue is that smtp:user@contoso.onmicrosoft.com
Is not being synched to O365.

Any known issue?

[#2]

@Marvin Oco 
Hey,

The .onmicrosoft address is an online attribut, and is not really related to any attribute in the on-prem Active Directory.
If you really need to change it, you need to stop Azure-AD Connect and make sure that the user object is "in-Cloud", edit the alias and then re-enable Azure-AD Connect.