question

Sebastian-9416 avatar image
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Sebastian-9416 asked YukiSun-MSFT commented

Outlook changes mail adress after sending

Hi,

we have a problem with an external user.
The company of the user changed the mail of all users in their company.

When user from our company send emails to the external user's new email address, the emails are send to his old email address.
His old email address is not existing anymore and therefore the postmaster sends a mail, that the mail couldn't be delivered.
In the postmaster mail it says: "The message you sent to <old email> couldn't be delivered due to: Recipient email address is possibly incorrect.

When we look in our "Sent Items" Folder in Outlook we can see the mail with the new email address of the user.
But the postmaster mail includes the old email address.

I isn't a user specific problem in our company.
When I sent my first mail to the new address of the external user from my own mailbox, I got the message from the postmaster too and the mails haven't reached the external user.

But the external user can send emails to users of our company.

The email addresses are not saved in ECP or local AD.
The only thing that is saved is the contact info of the B2B guestuser of the old email in Azure AD.
There is the old email as the primary email and the new email as the alternate email.
The proxy address is also the new email address.

Any ideas?
Is it even a problem at our company?

Thanks

office-exchange-server-administrationoffice-outlook-itpro
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Sebastian-9416 avatar image
1 Vote"
Sebastian-9416 answered YukiSun-MSFT commented

Hi,

I think I resolved the issue by myself.
Some minutes ago I deleted the old B2B guestuser of the old email address.
After that, everything worked again.

I am not an azure pro, therefore I can not explain, why exactly it works now or what was configured wrong.
But it was the only entry where the old and the new mail address were entered under the same item.

Summarized again:

Identity:
UPN: oldemail#domain.com@.... (not sure exactly, already deleted, but for sure the old email)

Contact info:
Email: oldemail@domain.com
Alternate Email: newemail@domain.com
SMTP: newemail@domain.com


Hope that helps someone in the future...

Thanks for your Answer @YukiSun-MSFT
Sorry for the Tags, it was my first question here in this MS FAQ.
I will keep it in mind for the next time.


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Hi @Sebastian-9416,

Great to see that you've sorted it out and really appreciate it for your sharing : )

By the way, you can click "Accept Answer" under your post so that it can make it easier for others who have a similar issue to see the useful information when reading this thread. Thanks!


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YukiSun-MSFT answered

Hi @Sebastian-9416,

But the external user can send emails to users of our company.

Are you able to sent out a "reply" to their emails by clicking "Reply" or "Reply All"?
May I know how did you enter the recipients' email address? What if typing the new email address manually and see if it works?

The only thing that is saved is the contact info of the B2B guestuser of the old email in Azure AD.

Are you in a Exchange hybrid environment?
All the external users you are having the issue with have been added as Azure AD B2B guestusers, right?

Regarding your concern about the old email saved in the guestuser contact info, sorry that the "office-exchange-server-administration" and
"office-outlook-itpro" tags mainly focus on questions related to administration for on-premise Exchange and general issues about Outlook client, and I personally know litte about the Azure AD B2B guest users. But during my research, I ran into the following thread under the tag "azure-ad-b2b":
how to update b2b user upn/mail ?
From the discussion there, seems like normally we would have to send an invitation again in order for the information to update.


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