but the other four doesn't say symantec
Are they the above registry entries, which won't go away?
This message has been processed by Symantec's AntiVirus Technology.
Unknown00000000.data was not scanned for viruses because too many nested levels of files were found.
This message may be just included with the email of the person, who is sending back the message, or even ISP.
Does your contact on the other end use Norton?
Ask them, if the above signature is included in your FIRST mail to them.