Mail originating from FreeBSD servers spam-blocked by large organization

[Alan Smithee]

Hi,

A friend works for a large organization, and a number of recent emails to
them from me were not received - and did not generate any sort of bounce
message.  After confirming successful delivery of these to their servers in
my logs and eliminating things such as mistaken inclusion of my server IP in
one of the black hole lists, we followed up with their administrators and
were told that a mail filter rule was in place to block and hold all
incoming email with the string 'freebsd' in the headers.

Naturally, this was rather disturbing, so we responded with an explanation
of how what FreeBSD was, how it is commonly used for legitimate email
servers by ISPs and companies, and how it is a relatively unlikely source
for email spam compared to (say) Windows.  To this we received a response
indicating that the security department of this organization had requested
this block, and that they felt that it should remain in place for the time
being.

The security department is responsible for protecting from everything from
standard worms and trojans to professional malicious attacks, and it is hard
to tell where on this scale their reasoning is for blocking email
originating from FreeBSD servers.  It is highly unlikely that they would
discuss any specific reasons.

Naturally, I think this is a rather draconian defense, of limited practical
use.  Please forgive the lack of detail about the organization in question,
and my use of a pseudonym for this email - the organization has some very
good reasons for being extremely careful about its security and would take a
dim view of having any of its measures discussed in public, even if they are
dumb ones.

Does anyone have any advice?  In particular, I would be keen to obtain any
statistics or references for organizations that use FreeBSD to host their
email servers.

Thanks,

An anonymous FreeBSD advocate (if that's not a contradiction in terms)