Email tests fail with "Error sending threepid validation email to testemail@example.com"

[anoadragon453]

The following tests seem to fail when running on some people's local machines:

• Can register using an email address
• Can login with 3pid and password using m.login.password
• After deactivating account, can't log in with an email

These tests run fine in CI, but locally they fail with the following stacktrace in Synapse's log:

2021-05-24 11:22:41,490 - twisted - 258 - INFO - sentinel - SMTP Client retrying server. Retry: 5
2021-05-24 11:22:41,491 - twisted - 258 - INFO - sentinel - SMTP Client retrying server. Retry: 4
2021-05-24 11:22:41,492 - twisted - 258 - INFO - sentinel - SMTP Client retrying server. Retry: 3
2021-05-24 11:22:41,492 - twisted - 258 - INFO - sentinel - SMTP Client retrying server. Retry: 2
2021-05-24 11:22:41,493 - twisted - 258 - INFO - sentinel - SMTP Client retrying server. Retry: 1
2021-05-24 11:22:41,493 - synapse.handlers.identity - 415 - ERROR - POST-16 - Error sending threepid validation email to testemail@example.com
Traceback (most recent call last):
  File "/home/callum/sources/synapse/synapse/handlers/identity.py", line 413, in send_threepid_validation
    await send_email_func(email_address, token, client_secret, session_id)
  File "/home/callum/sources/synapse/synapse/push/mailer.py", line 170, in send_registration_mail
    await self.send_email(
  File "/home/callum/sources/synapse/synapse/push/mailer.py", line 318, in send_email
    await self.send_email_handler.send_email(
  File "/home/callum/sources/synapse/synapse/handlers/send_email.py", line 85, in send_email
    await make_deferred_yieldable(
twisted.internet.error.ConnectionRefusedError: Connection was refused by other side: 111: Connection refused.

It appears that Synapse is unable to send an email through the fake SMTP server that Sytest spins up. I'm not sure whether this is due to the SMTP server failing to start/listen for connections (perhaps I'm missing a Perl or Python dependency?), or an issue with Synapse's configuration.

cc @richvdh as I believe he wrote the SMTP server impl. for sytest.

[govynnus]

I think it's to do with localhost resolving to IPv4, while the SMTP server listens on IPv6.

[govynnus]

Yep, all tests pass with:

diff --git a/tests/04mail-server.pl b/tests/04mail-server.pl
index 99d33e92..e118c5f0 100644
--- a/tests/04mail-server.pl
+++ b/tests/04mail-server.pl
@@ -33,6 +33,7 @@ our $MAIL_SERVER_INFO = fixture(
       $loop->add( $mail_server );

       $mail_server->listen(
+         family   => "inet",
          host     => $BIND_HOST,
          service  => 0,
          socktype => 'stream',

Related: matrix-org/synapse#7720

[richvdh]

that's odd. localhost should work over IPv6:

rav@fred:~$ ping6 localhost
PING localhost(ip6-localhost (::1)) 56 data bytes
64 bytes from ip6-localhost (::1): icmp_seq=1 ttl=64 time=0.079 ms

[govynnus]

It might be that my networking isn't set up quite correctly.

If I do ./run-tests.pl -w tests/11register.pl, then in a separate terminal:

$ telnet localhost <smtp_port>
telnet: can't connect to remote host (127.0.0.1): Connection refused
$ telnet ::1 46869
Connected to ::1
220 Sytest test server

[anoadragon453]

@govynnus Do you have:

::1        localhost

in your /etc/hosts file?

[govynnus]

Yep. ping6 localhost works fine.

[anoadragon453]

Is it worth trying to make Sytest listen on IPv4, or should we just track this in matrix-org/synapse#7720?

[richvdh]

If matrix-org/synapse#7720 is the only reason for the failure, I would rather see that fixed.

[clokep]

The upstream Synapse bug (matrix-org/synapse#7720) has been fixed. I'm going to close this with the assumption that it has fixed the sytest issue. If this is still seen when running sytest, please reopen.