Content-Type: multipart/mixed; boundary="001a1144413e115b8c055e744899"
   ...    
   </span></span>
   </body>
   </html>
   
   --001a1144413e115b87055e744897
   Content-Type: text/calendar; charset="UTF-8"; method=REQUEST
   Content-Transfer-Encoding: 7bit
   
   BEGIN:VCALENDAR
   ...    

   Content-Type: multipart/alternative;
   	boundary="_002_FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF_"
   ...    
   38zzLfaIt905RaHpwW10gxDaRM7fugsiycNfVW3ThPWAV0jAVl2v4DdneUk=
   
   --_002_FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF_
   Content-Type: text/calendar; charset="utf-8"; method=REQUEST
   Content-Transfer-Encoding: base64
   
   VKeoFC+u2MIsA+disK1yxSRWLpQJSbDdI1vXTzvVobC3rN+UqxzEd4HUhCnxlPH3rPFCuzefeDea
   ...

I need to filter calendar events. All such messages have an attachment with Content-Type: text/calendar. Here: http://forums.mozillazine.org/viewtopic.php?p=724059&sid=c5807de9790f2a3ac3c3ed36531297c4#p724059 I found that a body filter also applies to attacment headers. I created a test filter "Body contains text/calendar" with the action to mark matched messages as unread. When I run the filter on my inbox, only some calendar messages are affected: Here's an extract from a message that matches: Content-Type: multipart/mixed; boundary="001a1144413e115b8c055e744899" ... </span></span> </body> </html> --001a1144413e115b87055e744897 Content-Type: text/calendar; charset="UTF-8"; method=REQUEST Content-Transfer-Encoding: 7bit BEGIN:VCALENDAR ... And here's an extract from a message that does not match: Content-Type: multipart/alternative; boundary="_002_FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF_" ... 38zzLfaIt905RaHpwW10gxDaRM7fugsiycNfVW3ThPWAV0jAVl2v4DdneUk= --_002_FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF_ Content-Type: text/calendar; charset="utf-8"; method=REQUEST Content-Transfer-Encoding: base64 VKeoFC+u2MIsA+disK1yxSRWLpQJSbDdI1vXTzvVobC3rN+UqxzEd4HUhCnxlPH3rPFCuzefeDea ...