Shaw → Re: [ALL] Ask ShawSean

Never have I seen that. Pop uses 110 (Inbound), SMTP uses 25 (Outbound). I could change the ports, however it's a huge pain. I could also use a forwarding service, but that is another hop and another possibly place things can go wrong. Having everything unblocked and using default ports is easiest. For all that much work, rather just do a remote mail server.

SMTP uses port 25 for both directions. Email coming to your users will use inbound port 25, email being sent from your users uses outbound port 25 to connect to the remote mail server. POP3 (port 110) will be for your users to pick up their mail from you.
Your users could also use a 3rd party to send their outbound email.

As far as forwarding outbound SMTP via a 3rd party (IE shaw's servers), google "smarthost smtp". It does add a hop outbound, but it's far cheaper than upgrading my service to business and buying a static ip. I'm not running business services on it, just my own personal domain, and this setup has been working since they started blocking outbound port 25.

And again, Shaw only blocks port 25 outgoing. No other ports that I've noticed.

If you have a hosting service, it may offer this service for you already.

Mail relaying is a common service offered for free with domain hosting - these hosts require you to use Authenticated SMTP or Secure SMTP over ports like 587. Most MUAs can talk to this easily, and MTAs ought to be able to use it as well. These are allowed because they're authenticated - the mail sender has verified themselves to the relay so the email can be traced back to the origin.

A lot of incoming mail servers also block port 25 inbound from dynamic hosts - so Shaw's requirement of static IPs isn't unusual. So your options are to get a business package, or use your hosting service's mail relaying service.