You can enter any email address in that field:

any-user@any-domain.any-tld

Can be an alias, can be a catch-all email on your domain. Select the right email account (here, email account ≠ email address) with the right pre-configured credentials and that email will be sent, if not it will fail as it should.

It’s that simple and basic feature. But apparently email clients decided that’s not the right way and they make you pre-add every single bloody email address you ever want to use — this is specially painful for personal domains and catch-all addresses, especially the one-off ones.