Yet other SMTP 587 port email various errors

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Users discuss troubleshooting SMTP 587 port email errors during Discourse installation. Hyan notes that conflicting TLS settings — particularly DISCOURSE_SMTP_FORCE_TLS and DISCOURSE_SMTP_ENABLE_START_TLS — can cause errors like “TLS and STARTTLS are mutually exclusive” or “wrong version number”; setting DISCOURSE_SMTP_FORCE_TLS: false often resolves these. Another common issue is Net::SMTPAuthenticationError, which may stem from incorrect credentials or require setting DISCOURSE_SMTP_AUTHENTICATION: login. savionlee reports success with Mailgun by reversing those settings: DISCOURSE_SMTP_FORCE_TLS: true and DISCOURSE_SMTP_ENABLE_START_TLS: false, after encountering Net::ReadTimeout with ./discourse-doctor. They note the official troubleshooting guide didn’t help, but referenced threads — including one on port 465 issues — pointed them toward the correct configuration. ambimorph confirms that savionlee’s settings worked for them too, after a rebuild. The consensus suggests SMTP configuration is highly server-dependent, and default settings may need manual overrides — especially around TLS/STARTTLS — to resolve 587 port failures.

1

Different SMTP servers may occur different errors even with 587 port if testing with ./discourse-doctor

  1. TLS and STARTTLS are mutually exclusive
    This error has never mentioned in meta so far, you should set explicitly DISCOURSE_SMTP_FORCE_TLS: false otherwise it contradicts DISCOURSE_SMTP_ENABLE_START_TLS, as it is true by default. This may not always the case, but it’s worth a try.

  2. SSL_connect returned=1 errno=0 peeraddr=xxx.xxx.xxx.xxx:587 state=error: wrong version number
    Again, set DISCOURSE_SMTP_FORCE_TLS: false resolves the issue

  3. Net::SMTPAuthenticationError this can be caused by wrong username password of your credentials you set or can be resolved by setting DISCOURSE_SMTP_AUTHENTICATION: login

2

For Mailgun, on an fresh install i had to do:

DISCOURSE_SMTP_FORCE_TLS: true
DISCOURSE_SMTP_ENABLE_START_TLS: false

./discourse-doctor was reporting:

======================================== ERROR ========================================
                                    UNEXPECTED ERROR

Net::ReadTimeout

the whole troubleshoot document Troubleshoot email on a new Discourse install - documentation / sysadmin - Discourse Meta didn’t solve my issue.

Found this thread about amending it that would have helped me: Cannot send email - problem with port 465 - installation - Discourse Meta

Then found this Yet Another thread you posted that showed some flips for me to do.

3

This solution worked for me, followed by a rebuild.

Thank you!