Refs #127 -- Go even further with SMTP testing

src/pretix/base/email.py

@@ -0,0 +1,21 @@
+from smtplib import SMTPRecipientsRefused, SMTPSenderRefused
+
+from django.core.mail.backends.smtp import EmailBackend
+
+
+class CustomSMTPBackend(EmailBackend):
+
+    def test(self, from_addr):
+        try:
+            self.open()
+            self.connection.ehlo_or_helo_if_needed()
+            self.connection.rcpt("test@example.org")
+            (code, resp) = self.connection.mail(from_addr, [])
+            if code != 250:
+                raise SMTPSenderRefused(code, resp, from_addr)
+            senderrs = {}
+            (code, resp) = self.connection.rcpt('')
+            if (code != 250) and (code != 251):
+                raise SMTPRecipientsRefused(senderrs)
+        finally:
+            self.close()