if this is affecting your ablity to send email contact them. If on the other hand you are running a mail server and you should not be this might explain the blocked port? You have not really provided enough info to give a detailed answer
There is a service that uses another port(558 I guess, not sure). This is not widely available though 🙁 Some smtp servers might support this so check your documentation and of course, your ISP if they allow that, hihihi(they could also block that)…