You really cannot send mail to this domain if none of their MX hosts is listening on port 25.
However, what probably happened here is that your ISP blocks your outbound access to port 25 outside of their own network. This is basically the case everywhere; if you need outbound port 25, you need to be in a dedicated netblock, and probably pay more than you do for consumer broadband.
Your ISP's mail server will obviously have outbound access to port 25, and you should be able to use it as the relay host for your own outgoing mail.
Some services allow individual (usually authenticated) users to submit email on port 587 or 465, but to run an MX server, you need for it to listen on port 25.