Default domain clarification

Question

Default domain clarification

Email Administrator 1

Migrating from standalone mail server (Icewarp) to EOL. Have created and verified my domain (topperfloats.com) in EOL. MS domain (toppermail.onmicrosoft.com) is set as default domain and both are authoritative. The two mail servers will not be connected/related in any way.

All users use Thunderbird and I've successfully reconfigured my Thunderbird-Icewarp account to use the Icewarp server IP and created a TB user account to "toppermail.onmicrosoft.com" and have sent mail to/from gmail via the EOL-Thunderbird account. Have created my user accounts in the EOL topperfloats.com domain.

From a DNS perspective, what is the effect of making topperfloats.com the default? I'm trying to grok as many issues as I can before doing the cutover (<25 users) as EOL limits my ability to track down missing emails (compared to Icewarp). FWIW, no changes have been made to DNS yet. Thanks, Tom

Lucas Liu-MSFT 6,191 Reputation points

2021-03-15T09:12:35.203+00:00

Hi @Email Administrator ,
Do suggestions above help? If the issue has been resolved, please click “Accept as answer” to mark helpful reply as an answer, this will make answer searching in the forum easier and be beneficial to other community members as well.

Thanks for your understanding.

----------

If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.
Lucas Liu-MSFT 6,191 Reputation points

2021-03-19T07:38:55.073+00:00

Hi @Email Administrator ,
I am writing here to confirm with you how thing going now? If the above suggestion helps, please click “Accept as answer” to mark helpful reply as an answer.Your action would be helpful to other users who encounter the same issue and read this thread.
Thanks for your understanding.

----------

If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

2 answers

Your answer

Lucas Liu-MSFT 6,191 Reputation points

2021-03-15T09:12:35.203+00:00

Hi @Email Administrator ,
Do suggestions above help? If the issue has been resolved, please click “Accept as answer” to mark helpful reply as an answer, this will make answer searching in the forum easier and be beneficial to other community members as well.

Thanks for your understanding.

----------

If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.
Lucas Liu-MSFT 6,191 Reputation points

2021-03-19T07:38:55.073+00:00

Hi @Email Administrator ,
I am writing here to confirm with you how thing going now? If the above suggestion helps, please click “Accept as answer” to mark helpful reply as an answer.Your action would be helpful to other users who encounter the same issue and read this thread.
Thanks for your understanding.

----------

If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 1

Andy David - MVP 157.4K MVP Volunteer Moderator

You mean making it the default reply address for users?

If so,

Ensure you have DMARC and SPF and the MX records correctly set this domain to point to Office 365:

https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/use-dmarc-to-validate-email?view=o365-worldwide

Also be sure to enable DKIM for this domain as well (topperfloats.com)

https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/use-dmarc-to-validate-email?view=o365-worldwide#step-3-set-up-dkim-for-your-custom-domain

Once you do that, you will be good to go from a mail flow perspective.

Lucas Liu-MSFT 6,191 Reputation points

2021-03-05T08:08:41.097+00:00

Hi @Email Administrator ,
Agree with Andy.
SPF, DKIM and DMARC will protect your organization from receiving spam email. MX ensures that your organization can successfully receive mail. After you finish editing, please test the mail flow. And please make sure that the correct CNAME record is configured.

----------

If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

Email Administrator 1

Not about default reply address.

Question is about the ramifications of changing my domain (topperfloats.com) to the default in EOP. What happens under the hood?

Using this to setup DNS records:

https://learn.microsoft.com/en-us/microsoft-365/admin/dns/create-dns-records-at-dnsmadeeasy?view=o365-worldwide

Have not made the DNS changes yet as I want to make sure I understand how it all is going to work upon cutover. I don't like tracking down problems I didn't know were going to be problems. Hence, my question.

Andy David - MVP 157.4K Reputation points MVP Volunteer Moderator

2021-03-06T00:13:10.093+00:00

Where exactly are you changing this?
Lucas Liu-MSFT 6,191 Reputation points

2021-03-10T07:06:07.863+00:00

Hi @Email Administrator ,
If no changes are made to your MX records, the email sent to "topperfloats.com" will still be successfully sent to the user's mailbox.
In addtion, you also need to set the correct DMARC, SPF and DKIM as mentioned above.

----------

If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Share via

Default domain clarification

2 answers

Your answer