[SOLVED] Sending a verification email fails silently

Summary

I have setup a new instance of Mattermost CE 3.9.0 running in a Docker container and traffic is proxied through an Apache httpd.

When a verification mail is to be sent, the following is logged by Mattermost, but no email is received and there’s nothing logged about a related event on the mail server.

[2017/06/14 14:52:51 UTC] [EROR] /api/v4/users/login:Login code=401 rid=x5xx7745r7druy9qcwqtpxfxca uid= ip=1.2.3.4 Login failed because email address has not been verified [details: user_id=jkef95yhginwx84yajduk6ywza]
[2017/06/14 14:52:53 UTC] [DEBG] POST - /api/v4/users/email/verify/send

I can also see that the proxy seems to handle that request correctly, but a 200 is also returned when i deliberately set an invalid configuration value:

1.2.3.4 - - [14/Jun/2017:16:52:53 +0200] "POST /api/v4/users/email/verify/send HTTP/1.1" 200 421 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/58.0.3029.110 Chrome/58.0.3029.110 Safari/537.36"

I could verify in a openssl s_client session from within the container that I can send an email via SMTP with the parameters provided to Mattermost. We’re also running a Mattermost CE 3.6.2 on another host in a similar setup (w/o proxy) where the used SMTP account does work.

Is there a way to let Mattermost be more verbose when sending an email?

Thanks for your feedback @funkyfuture,

I’m going to close this issue off here as we can track it via the issue you opened on GitHub.