Rob Funk <rfunk(_at_)funknet(_dot_)net> writes:
That's a BIG "if". It's hard for most people to configure an MTA
properly. (Heck, for most people it's hard to configure them at all,
let alone properly.)
It depends on what MTA this is. People configure Exim or Postfix rather
quickly, and a safe MTA does not relay for foreigners either, and that's
about all that must be taken care of with modern software.
More current mail user agents
will only inject through SMTP, not through /usr/sbin/sendmail, so many
people have SMTP listeners.
Most people will (should) NOT have SMTP listeners. Most people will
configure their MUAs to send outgoing mail through their ISP's mail
server.
"Will not" is OK, "should not" is not. You don't decide, the user does.
Sure, but the average fetchmail user doesn't know or care about any of
that. And in my experience it's actually a challenge to get most MTAs
to listen only on localhost anyway.
Nope, it's trivial for all except sendmail.
Postfix:
vi /etc/postfix/main.cf
G O inet_interfaces= 127.0.0.1 Esc ZZ
qmail:
vi /service/qmail-smtpd/run
s/0/127.0.0.1/
ZZ
svc -t /service/qmail-smtpd
I'm confident it's also easy with Exim. It may be difficult with
Sendmail, I dropped that long ago.
Meanwhile, fetchmail's encouragement of a local SMTP listener
indirectly encourages spam-friendly mail relays.
Not at all. Only old and deliberately misconfigured software will relay
mail for strangers.
Of course, disabling the SMTP port and piping into the sendmail or
maildrop commands is a viable solution for many, if not most home-user
sites.
--
Matthias Andree