port 25 blocking may be circumvented using ssl(tls) access to smtp
server like one offered by gmail. Read the manpage of reportbug for its
command line options.
Many ISP now requests to use non-port 25 for outgoing mail. That may
be accomodated by specifying port on command line of report bug.
If you are totally isolated from IP network, you can still use reportbug
with e.g. -M option to start mutt. Then before sending the mail text
created, save mail text to a file and move it to other machine to send
it by mail or web mail.