MX record on sub-domain does not resolve correctly

[bjorn8]

Hi there,
I have a weird issue with an Microsoft 365 account on a sub-domain. I’ve been going around in circles with Microsoft support for weeks, but they are not very helpful.
We manage 100s of tenants in our Partner Portal and never had a problem like this.
We set up a 365 account and add a sub-domain to the account and then create a few email addresses on that sub-domain. The problem is that any email sent to those addresses does not resolve properly, although everything seems to be set up correctly. Microsoft says the domain is “healthy” and any MX record checker out there show the correct MX record.
The sub-domain is ma.instituteofhairandbeauty.com.au

Here is a sample bounce message I got sending an email from my personal account, but any email sent to the address gets the same bounce message after a while:

The sub-domain itself is connected to a Wix website via an A record. And that’s the same IP address I see in the bounce message. Maybe it has something to do with that?

[Laudian]

@bjorn8

The sub-domain itself is connected to a Wix website via an A record.

I’m afraid that is not correct. You have a CNAME record for ma.instituteofhairandbeauty.com.au, which means no other records for the same name are allowed.

dig +short ma.instituteofhairandbeauty.com.au
pointing.wixdns.net.
gcdn0.wixdns.net.
td-ccm-168-233.wixdns.net.
34.117.168.233

That is why the emails are sent to the IP of the CNAME record, not to the IP of your MX record.

[bjorn8]

Thanks Laudian,
Finally, someone who is giving me a helpful reply.
This is the first time we have an email setup on a sub-domain.
Would it work to change the CNAME to an A record so the sub-domain website still works, but the MX record would resolve properly?

[Laudian]

Yes, you’ll have to replace the CNAME with an A record if you want to receive emails on the same subdomain.

[bjorn8]

Thanks again Laudian,
I can confirm that this indeed solved the issue.
Cheers!