Sympatico bouncing email sent *to* my home server

I run a Debian-Sarge box that is permanently connected to the internet via DSL through execulink.com. I have registered a domain name for my computer (faustus.dyn.ca) with dyn.ca, a company in Halifax. The updater script runs once an hour; the dynamic IP address lease actually tends to stay the same for days at a time, so this is overkill.

My computer is set up to receive email directly, and this works perfectly for nearly everyone who sends me email. Anything sent to

arrives regularly and routinely.

Anything, that is, except email sent *to* faustus.dyn.ca *from* a Bell Sympatico account or from a domain called "transmedia". These emails get bounced back to the sender. (Outgoing mail to all addresses works fine.)

I don't myself have a Sympatico account, so I have no way of checking the bounced messages for an indication of why this is happening. The people who send me email from their Sympatico accounts are mostly Windows users and can't provide me with useful information derived from the bounces, except to say that Sympatico appears not to be able to find my hostname (faustus.dyn.ca). Since I can't verify this, I have no idea whether it is true or not.

I hate being imprecise and not providing adequate information, so consider this an exploratory opening post. I'd like to know whether anyone else has experienced similar problems with email sent from a Sympatico account to a host that uses a dynamically updated domain name.

I use exim4 as my MTA. It listens on the standard smtp port (25). Mail processing is done by a very vanilla procmail setup. I'm not currently running any spam blockers. The only possibly useful bit of information I can extract from my mail logs are lines like this:

H=bayc1-pasmtp02.bayc1-pasmtp02.bayc1.hotmail.com 65.54.191.162 P=esmtp S=1139 2005-09-05 13:46:22 1ECL2z-00014g-RW Completed 2005-09-05 13:48:23 SMTP data timeout (message abandoned) on connection from bayc1-pasmtp02.bayc1.hotmail.com 65.54.191.162

(I've replaced the real names with "username" in the above snippet for obvious reasons.) This doesn't make sense to me, since the log says "Completed", then registers an SMTP data timeout. However, is it possible that if I set the exim timeout value higher, I won't have this problem with Sympatico?

Lastly (and confusing the issue further), someone who normally uses Outlook Express and Sympatico, and who normally sends me html email (yuk!) sent me something as plain text--and it got delivered!

Thoroughly confused and annoyed,

-- Peter Schaffter Author of The Schumann Proof (RendezVous Press, Canada)