I spent a good chunk of time trying to figure out how to send mail from my local machine using my Dreamhost SMTP server as a smarthost. Here’s a sample setup using
defaults tls on auth on tls_trust_file /path/to/ca-certificates.crt logfile ~/.smtp.log account dreamhost host smtp.dreamhost.com port 465 tls_starttls off from email@example.com user firstname.lastname@example.org password yoursecretpassword account default : dreamhost
The important bit is
tls_starttls off, without which will lead to a whole world of frustration.