Update mail.py

should be .set_tos(), not .add_tos()

Author: richardbrockie

sgbackend/mail.py

@@ -68,7 +68,7 @@ def _build_sg_mail(self, email):
 
         # use smtpapi if recipient list provided, otherwise use standard to field
         if isinstance(email.to, list):
-            mail.smtpapi.add_tos(email.to)
+            mail.smtpapi.set_tos(email.to)
         else:
             mail.add_to(email.to)