diff --git a/dbmail/backends/mail.py b/dbmail/backends/mail.py
index 8f9ed82..afab24e 100644
--- a/dbmail/backends/mail.py
+++ b/dbmail/backends/mail.py
@@ -70,7 +70,7 @@ def _insert_mailer_identification_head(self):
     def _get_connection(self):
         if self._template.auth_credentials:
             return self._kwargs.pop('connection', None) or get_connection(
-                **self._template.auth_credentials)
+                **self._template.from_email.get_auth())
         return self._kwargs.pop('connection', None)
 
     def _get_template(self):
diff --git a/dbmail/models.py b/dbmail/models.py
index 00a225a..69ade02 100644
--- a/dbmail/models.py
+++ b/dbmail/models.py
@@ -98,8 +98,8 @@ def get_auth(self):
             return dict(
                 host=self.credential.host,
                 port=self.credential.port,
-                username=self.credential.username,
-                password=self.credential.password,
+                username=str(self.credential.username),
+                password=str(self.credential.password),
                 use_tls=self.credential.use_tls,
                 fail_silently=self.credential.fail_silently
             )