we use IIS 5.0 to relay e-mail to our Exchange 2000
server. During the relay it is filtered for Spam.  One
company cannot send us attachments and are using Exchange
5.5.  In the SMTP NCSA logs the ehlo, Rcpt, Mail From
commands come through with no problems, but once they send
the DATA command I receive "DATA
aaaaaaaaaaaaaaaaaaaaaaaaaaa - SMTP" 500 32, error. I have
no problems with attachments from any other source, and
they have no problems sending the attachments to any other
company, except ours. the attachment range
from .pdf, .xls, .doc, and .zips

The mail is never recieved by IIS correctly, so the spam
filter software does not appear to be a factor.  I can
bypass the IIS 5.0 relay server and receive the e-mail
just fine on our Exchange Box.  But this allows all the
spam to come through, not a popular option.

The problem comapany can send us e-mail with out
attachments with no problems.

From what I have found, the smtp error code 500 is a
syntax error, command unrecognized.  But, I have not found
what could be causing it.

Any information would be appreciated.

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