use a list for recipients rather than a string

src/teams/email.py

@@ -49,9 +49,7 @@ def send_new_membership_email(membership):
     return add_outgoing_email(
         text_template='emails/new_membership_email.txt',
         html_template='emails/new_membership_email.html',
-        recipients=', '.join(
+        recipients=membership.team.responsible,
-            [resp.email for resp in membership.team.responsible]
-        ),
         formatdict=formatdict,
         subject='New membership request for {} at {}'.format(
             membership.team.name,

src/utils/email.py

@@ -66,22 +66,19 @@ def add_outgoing_email(
     attachment_filename=''
 ):
     """ adds an email to the outgoing queue
-        recipients is a string, if theres multiple emails seperate with a comma
+        recipients is a list of to recipients
     """
     text_template = render_to_string(text_template, formatdict)
 
     if html_template:
         html_template = render_to_string(html_template, formatdict)
 
-    if ',' in recipients:
+    if not isinstance(recipients, list):
-        for recipient in recipients.split(','):
+        recipients = [recipients]
-            try:
+
-                validate_email(recipient.strip())
+    for recipient in recipients:
-            except ValidationError:
-                return False
-    else:
         try:
-            validate_email(recipients)
+            validate_email(recipient)
         except ValidationError:
             return False