Apart from MT integrating SMTP AUTH (please!) one thing you can do is sending the e-mail directly to the mailserver hosting your e-mail account. This one will always accept the e-mail…
This could get ugly when using a big mail provider with clustered/load-balanced mail servers, but should work usually…
If you use the smtp server you quoted and the email address you quoted as destination (to), that should work - this server is the destination mail server for that domain…
There should be no need for any authentication then.