[oclug]Blacklisted mail

[Hugh Campbell, Finlayson & Singlehurst]

Our office received the following reply to an email sent out yesterday:

= = = = = = = = QUOTE = = = = == = = = ==
This Message was undeliverable due to the following reason:

Each of the following recipients was rejected by a remote mail server.
The reasons given by the server are included to help you determine why
each recipient was rejected. 

    Recipient: <sdc at arkpatent.com>
    Reason:    Mail rejected - you are listed in OsiruSoft's Spam Stopper 
(Spam) [FREE] - http://relays.osirusoft.com/
= = = = = = = = END OF QUOTE = = = = == = = = ==

I have checked the databases available through http://relays.osirusoft.com 
(the address mentioned in the returned message above), and neither my IP 
nor my mail address (nor the recipient's) is found in any of the black list 
databases.

We _do_ have an internal mail server, but it is not visible to the outside 
world, and relay requests are restricted to identified clients on the local 
LAN.  The internal server fetches and receives mail from our external ISP 
mail account, so that it appears to our ISP as a single machine using our 
single e-mail address.  We only have one e-mail address, and the mail is 
sorted internally using additional criteria to get back to the proper user.

I have never seen this message before, and I haven't e-mailed this person 
before.  The message seemed to indicate that it was a problem with the 
recipient (ie the _recipient_ was rejected), but his email addresses (both IP 
and DNS) also check clean in the blacklist databases (at least as viewed 
through the Osirusoft site)

Anyone have any idea what has happened here? 

Hugh