Before you use your domain with Office 365, we have to make sure that you own it.
Your ability to log in to your account at your domain registrar and create the DNS record proves to Office 365 that you own the domain.
For information about how your email is protected with EOP, see Exchange Online Protection overview. Check out the Introduction: Office 365 mail flow basics topic.
We especially recommend reading the part about SPF records because customers often list the wrong values in their SPF record, which can cause mail flow problems.
If you’re having trouble with mail flow or other issues after adding DNS records, see Troubleshoot issues after changing your domain name or DNS records.
In the fields I entered: Name: mail Data: 2.20 Done. If you use an external mail agency, they may suggest other values, in which case, follow their advice. Now we only need to wait for the DNS records to propagate.
However, it would be nice to check the records are correct and we haven't made a typo somewhere.
If you use an external mail agency (such as fusemail or fastmail), then leave out the A-record creation and point the MX record as directed by your provider.
So, log into the Slice Manager at https://manage.and navigate to the DNS tab: Now click on the 'records' link next to your domain.
You create new MX records, or change their priority, in order to change how email is processed for the domain.