diff --git a/addons/mail/wizard/mail_compose_message.py b/addons/mail/wizard/mail_compose_message.py
index f9e3ff52f28..d7d5ae9bae1 100644
--- a/addons/mail/wizard/mail_compose_message.py
+++ b/addons/mail/wizard/mail_compose_message.py
@@ -19,6 +19,7 @@
 #
 ##############################################################################
 
+import base64
 import re
 
 from openerp import tools
@@ -261,7 +262,6 @@ class mail_compose_message(osv.TransientModel):
 
             for res_id, mail_values in all_mail_values.iteritems():
                 if mass_mail_mode and not wizard.post:
-                    # process attachments and attachment_ids before sending values to mail_mail.Lcreat
                     m2m_attachment_ids = self.pool['mail.thread']._message_preprocess_attachments(
                         cr, uid, mail_values.pop('attachments', []),
                         mail_values.pop('attachment_ids', []),
@@ -306,7 +306,12 @@ class mail_compose_message(osv.TransientModel):
             if mass_mail_mode and wizard.model:
                 email_dict = rendered_values[res_id]
                 mail_values['partner_ids'] += email_dict.pop('partner_ids', [])
-                mail_values['attachments'] = email_dict.pop('attachments', [])
+                # process attachments and attachment_ids before sending values to mail_mail.create()
+                attachments = []
+                if email_dict.get('attachments'):
+                    for name, enc_cont in email_dict.pop('attachments'):
+                        attachments.append((name, base64.b64decode(enc_cont)))
+                mail_values['attachments'] = attachments
                 attachment_ids = []
                 for attach_id in mail_values.pop('attachment_ids'):
                     new_attach_id = self.pool.get('ir.attachment').copy(cr, uid, attach_id, {'res_model': self._name, 'res_id': wizard.id}, context=context)