= Postfix =

If you are running postfix on a residential machine and wish to send
through your ISP's mailserver, the settings in main.cf are documented
in [http://www.postfix.org/postconf.5.html] under 'smtp_tls_wrappermode':

smtp_tls_security_level = encrypt
smtp_tls_wrappermode = yes

This requires cyrus_sasl, and for some ISPs (hello, virginmedia) you
will need to use port 465 in your sasl commands.

A few other servers may still reject you mail, but most will not flag
it as spam.