By storing the PidTagCreatorName on creation and checking when trying to edit or delete an specific message.
Monotone-Revision: 905276f295d6f28a6946297f6a7af9ad60f71842 Monotone-Author: wsourdeau@inverse.ca Monotone-Date: 2012-06-29T17:59:38 Monotone-Branch: ca.inverse.sogo