Ben Scott dragonhawk at
Tue Mar 7 17:51:02 EST 2006

Technical solutions.  Getting your mail to go through when your IP
feed is blocking TCP port 25 outbound.

(1) Get an IP feed that doesn't have the restriction.

(1) (a) Get your provider to grant you an exception under you existing
service plan.  Most won't do this for free, but hey, it's worth a try.

(1) (b) Switch to a provider/plan/etc that doesn't restrict what you
can do as much.  This will often cost more, but often yields
drastically better customer service as well.

(2) Relay all your mail through your IP feed's local SMTP relay.

(3) Relay all your mail through a non-local relay listening on a different port.

(3) (a) RFC-2476 defines the concept of a "Message Submission Agent",
or MSA.  MSA is basically a subset of SMTP designed for submitting new
mail to a more intelligent system.  TCP port 587 is the IANA reserved
number for this.  Authentication is generally required, thus this is
currently seen as not-a-threat for spam.  Many modern systems are
pre-configured to provide this service.  You may thus be able to relay
through another server, on a "commercial" feed, with minimal config

(3) (b) On any available host you have access to, configure a listener
on any convenient port to provide authenticated SMTP relay.  Many ISPs
which provide mail hosting independent of Internet feed include such a
service.  If your IP feed loves to block lots of ports, port 80 will
almost always work.

(4) Relay all your mail through a non-local relay listening on the
standard port 25, but use a VPN or some other tunnel mechanism to get
there.  This is useful if you have a configuration you don't want to
disturb for some reason, or just want to avoid the hassle of worrying
about what your SMTP relay should be depending on where you are.

(5) Use VPN/SSH/HTTPS/VNC/X11/etc to access a mail system running
elsewhere, and use that mail system remotely.  Your IP feed only
carries your remote access traffic.  Not usually what people are
looking for, but worth mentioning.  Webmail falls into this category.

-- Ben

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