Dear Giles, I think you're searching for this. $ cat /etc/postfix/main.cf myorigin=yourdomain.com relayhost=your.smarthost.com smtp_sasl_auth_enable=yes ## you probably want to limit how postfix authenticates # smtp_sasl_security_options=noanonymous # smtp_sasl_mechanism_filter=login smtp_sasl_password_maps=hash:/etc/postfix/relay_password ## if something doesn't work and you need detailed(!!) logs #debug_peer_list=your.smarthost.com #debug_peer_level=3 smtp_use_tls=yes #inet_interfaces = loopback-only #local_transport = error: disabled unknown_local_recipient_reject_code = 450 $ cat /etc/postfix/relay_password your.smarthost.com yourusername:yourpassword $ postmap /etc/postfix/relay_password $ service postfix reload You can check out the commented option in the man pages or http://www.postfix.org/postconf.5.html if you're interested later/have some spare time/if it doesn't work ;-) Brgds -- Freundliche Gruesse/Best Regards Benjamin Hackl IT/Administration Media FOCUS Research Ges.m.b.H. Maculangasse 8, 1220 Wien Austria Tel: +43 1 258 97 01-295 b.hackl at focusmr.com