I've created an RSA keypair that I used for SSH, and it includes my email address. (At the end of the public key.)
That part of an ssh key is just a comment. You can change it to anything you want at any time. It doesn't even need to be the same on different servers. You can remove it as well. It is only there to help you or someone else figure out what to delete when you have many keys in an authorized_keys file and you need to revoke or change one of them.
ssh-rsa AAAAB3N....NMqKM= this_is_a_comment
When I create my keys with ssh-keygen I usually use a command like this to set a different comment. I don't think the username@host is very useful. You can certainly put it whatever comment that you like that will be useful to you and any other admins to help identify who the key belongs to.
ssh-keygen ... -C YYYYMMDD_surname_givenname