Mails to Google being blocked for illegal attachments

[lists at foks.se (foks)]

Hello,

Since Sep 7 Google has bounced a specific type of our mails with this
message:

host aspmx.l.google.com[74.125.43.27] said: 552-5.7.0 Our system
detected an illegal attachment on your message. Please 552-5.7.0 visit
http://mail.google.com/support/bin/answer.py?answer=6590 to 552 5.7.0
review our attachment guidelines. z4si211085bkd.116 (in reply to end of
DATA command)

The only attachment is a gif image so it seems that Googles check is
wrong. Has anyone experienced this issue, or has any helpful contact
information to Google? I have checked
http://www.google.com/support/a/bin/static.py?page=contacting_support.ht
ml and called these numbers, but they were not able to help me.

Regards,
J?rgen Nilsson