Proxy Connections to lotus

How i should to configure my domino server to have a connection with another as example smtp server? Do i have to open any advance port in my http proxy (25 smtp, 110 pop3, 143 imap, 1080 socks) or lotus domino can connect through only http port?

Thank you.

Subject: ports to open …

Only port 25 should be open if you are using smarthost as relay …