diff --git a/addons/mail/models/mail_template.py b/addons/mail/models/mail_template.py
index a98c2d99df87f5b5bffe5db2ae538c0c4bb47115..d4c7edee93110ac20b8a8f9a0da26cc307641a10 100644
--- a/addons/mail/models/mail_template.py
+++ b/addons/mail/models/mail_template.py
@@ -176,7 +176,7 @@ class MailTemplate(models.Model):
             partner_to = values.pop('partner_to', '')
             if partner_to:
                 # placeholders could generate '', 3, 2 due to some empty field values
-                tpl_partner_ids = [int(pid) for pid in partner_to.split(',') if pid]
+                tpl_partner_ids = [int(pid.strip()) for pid in partner_to.split(',') if (pid and pid.strip().isdigit())]
                 partner_ids += self.env['res.partner'].sudo().browse(tpl_partner_ids).exists().ids
             results[res_id]['partner_ids'] = partner_ids
         return results