Changed some users email domain. How long will it take until emails start arriving in the new domain?

Pitawat-MKV 10

Previous Microsoft 365 admin resigned from the company. I took over without knowing there was an old domain, say olddomain.com, that was used for a small number of users. It seems like when they migrated to a new domain (newdomain.com), the previous admin set alias for these users to use new domain, but they were still actually on olddomain.com as primary domain.

Now olddomain.com expired and emails for these users stopped working so I went to Microsoft 365 admin center > Settings > Domains > olddomain.com > Users > Check all users > Change domain and select newdomain.com and save.

I also did the same on olddomain.onmicrosoft.com and change their domains to newdomain.onmicrosoft.com.

It's been overnight and some emails from external senders are still not arriving in newdomain.com domain for those users. I suspect that there are some caching somewhere that cause emails to still being sent to olddomain.com.

This is causing some interruptions in productivity and I don't know how long it will be like this, or is there anything else I can do to solve this?

Thanks.

1 answer

Yuki Sun-MSFT 41,201 Reputation points Microsoft Vendor

2023-12-20T07:56:00.31+00:00

Hi @Pitawat-MKV ,

Please make sure that the MX record for the new domain has been updated properly. And then according to the document below, it can take up to 72 hours for the DNS changes to take effect and seems that there's no way to work around this. So, you may still need to wait for some time.

Email messages aren't received for a new domain that you add in the Microsoft 365 portal

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Pitawat-MKV 10 Reputation points

2023-12-20T09:31:37.01+00:00

Hello @Yuki Sun-MSFT

Apologies for the confusion. The new domain has been in use many months ago and most of our users are already on that domain from the beginning without any issue.

I have not made any changes or added a new domain to Microsoft 365 admin center. I have only changed some users' domain to another domain and it seems that some emails from external senders are still being delivered to the old domain.

Thank you.

Yuki Sun-MSFT 41,201 Reputation points Microsoft Vendor

2023-12-20T09:46:35.8133333+00:00

Hi @Pitawat-MKV ,

I have only changed some users' domain to another domain and it seems that some emails from external senders are still being delivered to the old domain.

Thanks for the clarification. Just wondering did you keep the old email addresses as the alias? If not, it's suggested to add them back as the additional email addresses to see how it goes. See this link.

If the issue persists, did the external senders receive any NDR? If yes, could you share the error message in the NDR after removing personal information so that we can see if more clues can be found?

Pitawat-MKV 10 Reputation points

2023-12-21T03:31:22.02+00:00

Hi @Yuki Sun-MSFT ,

As I mentioned in the question, the old domain is expired and we didn't renew it. Thus, the DNS of the old domain doesn't work anymore. Is this what causing the problem? If yes, how can we make it switch to the new domain and when can we abandon the old domain? I don't want to have 2 domains forever.

I asked a couple of senders to manually type in the correct email address with the new domain and the email was still being delivered to the old domain and thus not being delivered to the correct inbox, or sometimes it just got missing.

Some senders received the NDR email, and I believe some didn't. From the NDR email, sometimes it says "Delivery has failed to these recipients or groups: xxxx**@newdomain.com**" while some NDR says "Delivery has failed to these recipients or groups: xxxx**@olddomain.com**"

I'm not sure why some emails are using old domain and while some are using new domain but still not being delivered.

Thank you.

Yuki Sun-MSFT 41,201 Reputation points Microsoft Vendor

2023-12-21T07:39:36.3966667+00:00

Hi @Pitawat-MKV ,

I reviewed your original post along with the additional information shared in the comments and now realized that the new domain should have already been set up properly in both DNS and your organization, otherwise it wouldn't have been worked fine for part of the users. I apologize for the incorrect information that was given earlier, due to my misunderstanding of the situation.

When it comes back to the issue, considering that the old domain is no longer working any more, it's expected that mails to the old domain email address cannot arrive. But for the new domain email address, my understanding is that, even if you didn't change anything, it should work when the external sender manually typing the new domain email address into the To field, because the new domain address is existent as an alias of the recipient. Did you have a chance to try asking an external sender to manually entering the new email address prior to changing their email address and did that work?

I tried searching around but so far haven't seen information about whether it require any downtime for a new primary email address to start receiving mails. But per my understanding, it might be similar to scenario where a new alias is added. According to this article, it may take up to 24 hours for a new alias to update in Microsoft 365:

I can understand that you have already waited overnight, but could you confirm if it has exceeded 24hours?

As regarding the NDR message, can you check it again to see if there's any more information like the error code with description for further researching? See this link for samples of NDR error code.

Pitawat-MKV 10 Reputation points

2023-12-22T05:20:45.9133333+00:00

Hi @Yuki Sun-MSFT ,

Did you have a chance to try asking an external sender to manually entering the new email address

Yes, I asked some senders to manually type the correct email address but it's still got delivered in the old domain, as mentioned in my comment above.

I can understand that you have already waited overnight, but could you confirm if it has exceeded 24hours?

Yes, it's been a couple days since I updated the alias email of those affected users. Right now the alias are user@newdomain.com and user@newdomain.onmicrosoft.com. No old domain is in the alias anymore.

can you check it again to see if there's any more information like the error code with description for further researching

The error code is 10061 which is "Connection refused". The NDR says that olddomain.com is refusing connection which is expected because this domain isn't in use anymore. The question is why are those emails still being routed to olddomain.com despite the senders entered newdomain.com address?

Thanks.

Yuki Sun-MSFT 41,201 Reputation points Microsoft Vendor

2023-12-25T07:26:22.4466667+00:00

Hi @Pitawat-MKV ,

The question is why are those emails still being routed to olddomain.com despite the senders entered newdomain.com address?

This is indeed weird. Can these users receive internal mails properly?
Any clues in the message trace?

I'd also suggest checking if there's any mailbox forwarding configured for these users:

get-mailbox user1 | fl *forwarding*

Yuki Sun-MSFT 41,201 Reputation points Microsoft Vendor

2023-12-27T01:40:34.52+00:00

Hi @Pitawat-MKV ,

Another thought is to contact the DNS provider of your new domain and check if there's any forwarding rule implemented there.

Pitawat-MKV 10 Reputation points

2023-12-28T08:24:10.9966667+00:00

Hi @Yuki Sun-MSFT ,

Thanks for your comments. I have opened a ticket to Microsoft Support and have been working with them for the past several days. Right now the solution that I was given is that the recipients were added as guest users in the sender's Entra ID under the old domain.

We are working with admins of that organization to delete guest users under old domain and will try sending emails to the problematic recipients again. I will update here if it's working.

Yuki Sun-MSFT 41,201 Reputation points Microsoft Vendor

2023-12-28T09:16:12.8033333+00:00

Hi @Pitawat-MKV ,

Thanks for sharing these updates with us! And hopefully the issue can be resolved by deleting the guest users under old domain.
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Changed some users email domain. How long will it take until emails start arriving in the new domain?

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