Issues with adding @mydomain.onmicrosoft.com proxyaddresses

[Joonas Heikkinen]

Greetings,

I have been struggling with this proxy address issue during the past few days and can't seem to find a way around it. Hope you guys can help. So the issue is I'm not able to add @mydomain.onmicrosoft.com proxyaddress entries to my Exchange Online mailboxes. Can't do this from the cloud (users are read-only) or through on-premise AD.

Here's an example: 

- Adding a proxyaddress smtp:john@mydomain.com to local AD works. This entry syncs to the cloud.

- Adding a proxyaddress smtp:john@mydomain.onmicrosoft.com to local AD doesn't get synchronized.

There's no on-premises Exchange set up if that makes any difference.

Any help would be much appreciated!

[#2]

Hi Joonas,

Have you extended your local AD with Exchange properties ?

In your AD Connect do you have selected Hybrid ?

You will need both to the extended properties of local AD object to be synchronized to Azure AD and Exchange Online.

[#3]

Thanks for the tips, I'm gonna look into it now.

Cheers,
Joonas

[#4]

From the On-premise Exchange have you tried?

Enable-RemoteMailbox user -PrimarySmtpAddress first.last@domain.com -RemoteRoutingAddress user@domain.mail.onmicrosoft.com ?

[#5]

I have same problem. Did you find a solution for this problem?

[#6]

Hello..

I had the same issues which I could able to resolve.. Firstly, Alias in office365 is synced from mailnickname in onprem AD and appends the onmicrosoft domain. Also, alias in O365 will get synced from onprem AD only once as per the microsoft design so we can't rename later. However, there is a workaround to fix this issue.

1) Rename the mailnickname from SamAccountName to UPN prefix
2) Move the user to lostandfound OU or Any OU which is not under Azure AD Connect sync scope
3) Run the sync manually using the command Start-AdSyncSyncCycle -PolicyType Delta
4) Once sync is completed, the user will get deleted from Azure AD. So login into Office365 Admin center and open the deleted Users... Restore the user which you are targetted(you can choose the password)

5) After restoring the user, user became cloud user so assign any license to appear the user in exchange admin center.

6) Since the user is not synced from onprem AD and became cloud user, rename the alias as you wish

7) Now move the user back to same OU where it was earlier.

8) Run the delta sync again.

9) Now the restored user becomes on prem AD.