Login with another domain than connecting to on XMPP

I have an account on an XMPP that allows me to connect to a clearweb address as well as a .onion address, however when logging in it distinguishes between users of @clearweb and @dotonion. I should be able to connect to dotonion and login with username@clearweb.

I can only specify username and domain in account preferences of tor-messenger. Thus my login credentials are locked to username@dotonion and connecting to dotonion. Whereas I'd like to be able to connection dotonion but use username@clearweb as my login.

Trac:
Username: rel