I have an Ubuntu server and I have various needs to send email from it (automysqlbackup, other scripts, mantis bug tracker) but it has access to internet only using a proxy. Postfix or anything else, as long as I'm able to send mail, it's perfect.
I could use Squid or Astaro Security Gateway, since we have two proxies on this network...
The easiest the best :)
Thanks a lot!