Yeah, I do the same - I plugged in Postfix, Dovecot and SpamAssassin and haven't had to touch it other than occasionally confirming backup scripts and automatic security updates are working.
I do something similar, but when I send an email to a person for the first time, it always ends up in the spam folder by GMail.
Taken from my smtpd.conf:
table secrets { mylogin = [email]@ziggo.nl:[pass] }
accept tagged DKIM for any relay via tls+auth://mylogin@smtp.ziggo.nl:587 auth <secrets>It kind of defeats the purpose, since now the third-party will be able to read all my outgoing emails, and have control over them.
Relaying via the ISP's mail server though (even with TLS) seems like it would disclose the message contents.