User unable to receive external emails after changing the last name (email)

Bronze Contributor


we have a user who changed his last name, and for that reason we changed the last name and email address in Active Directory in hybrid mode (I mean the SMTP address in the ProxyAddress attribute).

Changes are properly synchronized and visible in Azure AD, Microsoft 365 and Exchange Online.

After this change, the user is unable to receive external emails (he can only receive emails from our domain). All other users regularly receive emails, so this user is an isolated case. We have had surname changes before and everything worked properly.

Neither UPN nor SAM Account was changed for the user, only the primary SMTP address. All settings related to receiving external emails for the user have been checked and no forwarding rule has been included.

When an e-mail is sent to the user from an external e-mail, we receive a message about the impossibility of delivering the e-mail.

Does anyone have any idea why the user does not receive external emails after changing the last name and email?

Kindest regards


5 Replies
Did you check if the primary email address exists somewhere else? As a proxy address on another account e. g.

Hi @wmkwi,

thanks for your solution, I have checked if the primary email exists somewhere else and the answer is no.

This email address is being used (or exists) just for that user.

Kindest regards


@LeonPavesic Who is generating the NDR? What does it say? I'm on-prem admin only so I'm not aware of any hybrid issues like that. Check twice, if the address is written correctly, that it is identical in Exchange (EAC/Get-Mailbox) and AD/AzureAD.


When changing the name via EAC email flow should work properly.


Hope you'll find a hybrid experienced admin here. :)

Hi @wmkwi,

our server is generating thr NDR messagge.

The email is the same on-prem and in Azure (also in Exchange Online). 

We checked every attributes and settings in AD, Azure and Exchange. The user still cannot recieve external emails, just internal from out domain. 

Anyone else maybe have experience or a solution with this case?

best response confirmed by LeonPavesic (Bronze Contributor)
The issue was resolved by deleting the SMTP primary address in Active Directory, syncing, and adding the same SMTP primary adress.