postfix enabled, but port 25 stays disabled ?!

[Eduard Hoenkamp]

Postfix replaced (or rather was added to) sendmail in 10.3 Yet, port 
25 seems disabled be default (it was enabled in 10.2.x). That means I 
can send mail, but only receive mail sent on the same host. Many 
sites mention this problem, but I don't see any solution posted.

Anyone knows how to enable port 25? Please reply only if
   telnet <here-your-10.3-host> 25
is not refused. Thank you, Eduard.