Summary: If you have an account, you can send email to, and the email will be delivered to account.

This is very useful if you are using your own domain, and need to migrate from an existing system to FastMail in a staged approach. You can add the domain at FastMail, add the accounts & aliases in that domain, but while the domain is still pointing to the old server, you can setup forwards from the old system to the same names, but hosted at the FastMail server via the forwarding tunnel approach above.

For example, say you have the domain with 100 users already at an existing provider, and you want to setup a FastMail business account and move the existing users to FastMail. You want to move one user at a time starting with the user

So you signup a FastMail business account, and add the domain to it and activate the domain by changing the MX record for to point to us. You then create the user Now because the domain still points to the existing server, any email sent to will go to the existing system. To actually forward it to FastMail, you setup a forward at the existing system so any email arriving for is forwarded to Now any email that arrives for at the existing system will be forwarded to the account at FastMail.

You can then repeat this process for each existing account, and when all accounts are done, you can switch the MX records for the domain to point to our servers and the transition will be complete and seamless.