If you are saying you can’t because your ISP blocks port 25 there are a few solutions that you can use that are free as long as you don’t send or receive over 2000 emails a month or something like that. I have used both of these solutions with my last ISP since they blocked port 25. I used http://ghettosmtp.com as a relay server. Wesley, the provider of the service is a pretty neat guy. I used https://www.smtp2go.com as my external outbound relay. They both worked great as a work around. I have ATT fiber now and 25 was blocked until I called in and requested it to be unblocked.

Anyways, I hope that helps. Let me know if you have any questions!