In order to use Mimecast for your email service, you first need to add any domains you want to use with it. In addition, you must prove that you own the domain before you will be able to use it for the Mimecast service.
Add a Domain
Adding a domain is completed through your Mimecast Admin Console, for which you will need to have the Basic Administrator role or greater, or have the “Directories Menu > Internal > Register New Domain” permissions granted.
Note: Depending on your domain host, it may take some time for the record to be accepted. You can return to this screen later by going to ‘Administration > Directories > Internal Directories’, then selecting ‘View > Pending Domains’ and selecting the domain.
Once you’ve added a domain to Mimecast, you should ensure that any existing policies are extended to cover the new domain, specifically the Delivery Routing policies.
Only once you have your policies and addresses added, should you change your MX Records.
Remove a Domain
Only a Super Administrator can remove a domain from your account. If you don't have a user with this role, please contact us at firstname.lastname@example.org to request the removal.