[FIX] mail: Speep improvement when sending email using 'Send by Email' wizard. (Maintenance Case: 606994)
Merge pull request #471 from odoo-dev/7.0-opw-606994-rgo

[MERGE] mail: Speed improvement, backport of rev ed116d6b6b5ab5e4436cce5b6da078417e0a9efc