No, just running some quick tests against the heroku proxy (proxy.heroku.com) I can only make connections to ports 80 and 443. Being as heroku don't provide any POP/SMTP it doesn't make sense for them to have those ports open I'm afraid.
Heroku's mail services? Yes, check out the "Add-On" link for cloudmailin, mailgun and sendgrid. Basic service is free (they still want your credit-card and hope you exceed free quota).