Add management command to test sending email.

Fixes: #622.

[With cleanups/doc tweaks by tabbott]

README.prod.md

@@ -148,8 +148,11 @@ need to do some additional setup documented in the `settings.py` template:
 
 * For Google authentication, you need to follow the configuration
   instructions around `GOOGLE_OAUTH2_CLIENT_ID` and `GOOGLE_CLIENT_ID`.
+
 * For Email authentication, you will need to follow the configuration
-  instructions around outgoing SMTP from Django.
+  instructions for outgoing SMTP from Django.  You can use `manage.py
+  send_test_email username@example.com` to test whether you've
+  successfully configured outgoing SMTP.
 
 You should be able to login now.  If you get an error, check
 `/var/log/zulip/errors.log` for a traceback, and consult the next

zerver/management/commands/send_test_email.py

@@ -0,0 +1,21 @@
+from __future__ import absolute_import
+
+from django.core.management.base import BaseCommand, CommandError
+from django.conf import settings
+from django.core.mail import send_mail, BadHeaderError
+
+class Command(BaseCommand):
+    help = """Send email to specified email address."""
+
+    def add_arguments(self, parser):
+        parser.add_argument('to', metavar='<to>', type=str,
+                            help="email of user to send the email")
+
+    def handle(self, *args, **options):
+        subject = "Zulip Test email"
+        message = "Success!  If you receive this message, you've successfully " + \
+            "configured sending email from your Zulip server."
+        sender = settings.DEFAULT_FROM_EMAIL
+        to = options['to']
+
+        send_mail(subject, message, sender, [to])

zproject/local_settings_template.py

@@ -61,6 +61,9 @@ SSO_APPEND_DOMAIN = None
 # that account as "less secure":
 # https://support.google.com/mail/answer/14257.
 #
+# You can quickly test your sending email configuration using:
+#   ./manage.py send_test_email username@example.com
+#
 # A common problem is hosting providers that block outgoing SMTP traffic.
 #
 # With the exception of reading EMAIL_HOST_PASSWORD from