I have an VPS with which I run my own email server sitting out in the ether of the internet which I have SSH access to. My my logging shows I'm getting 500 or so failed attempted connections per day and so I would like to close the default SSH port and open an alternative and I would like to access my SMTP service from an additional port as my ISP blocks port 25.
The server is Debain Squeeze running Postfix and OpenSSH and using Shorewall as the firewall.
Assuming the above is considered good practice (if not, please advise me on how I should achieve my objectives), should I use port forwarding on my firewall or have the services run on alternative ports and open/block the appropriate ports using the firewall? Specifically I'd like to know why one method is preferred over the other.