Mails to Google being blocked for illegal attachments

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, Jörgen Nilsson