I have several inbound messages that get bounced with the error message in the title. Sometimes they get through from the same sender and sometimes they do not. They are all on the same domain (not ours). It is not an attachment size issue and our DNS and SPF record shows no errors according to MXToolbox (itnet.ca) and well as we are on no blacklists as of this morning. Our connection is an unfiltered and unmanaged OC3. All SMTP traffic goes through a Symantec Brightmail gateway then onto the Exchange server on the same subnet. I have disabled DNS lookup on all the individual filters in Brightmail but left the main entry for DNS lookup intact. Any help would be greatly appreciated.