Steps to reproduce the problem

Case 1) In the script:

1. Follow steps on joinmastodon.org to install mastodon and prerequisites from source
2. run RAILS_ENV=production bundle exec rake mastodon:setup
3. attempt to configure with any SSL related authentication setting

Case 2) In a running mastodon instance have in the .env.production file the standard settings using port 465 / SSL:

SMTP_SERVER=mymailserver
SMTP_PORT=465
SMTP_LOGIN=myloginemail
SMTP_PASSWORD=mypassword
SMTP_AUTH_METHOD=plain
SMTP_OPENSSL_VERIFY_MODE=client_once
SMTP_ENABLE_STARTTLS=always
SMTP_FROM_ADDRESS=notifications@emailaddress

Expected behaviour

An email should be generated and successfully sent

Actual behaviour

The commands timeout and produces: "Net::ReadTimeout: "Net::ReadTimeout with #TCPSocket:(closed)" in script output and syslog

Detailed description

To resolve this problem we consulted this discourse link:
https://discourse.joinmastodon.org/t/new-mailserver-no-mails/3420

The problem appears to be in the SSL settings. SMTP_AUTH_METHOD, SMTP_OPENSSL_VERIFY_MODE and SMTP_ENABLE_STARTTLS are commented out and SMTP_TLS=true must be added.

My successful settings were:

SMTP_SERVER=mymailserver
SMTP_PORT=465
SMTP_LOGIN=myloginemail
SMTP_PASSWORD=mypassword
#SMTP_AUTH_METHOD=plain
#SMTP_OPENSSL_VERIFY_MODE=client_once
#SMTP_ENABLE_STARTTLS=always
SMTP_TLS=true
SMTP_FROM_ADDRESS=notifications@emailaddress

Related Mastodon Thread:
https://mstdn.ca/@chrisale/109725219048851990

Specifications

Debian 11
Mastodon | 4.0.2
Ruby | 3.0.4p208
PostgreSQL | 15.1
Redis | 6.0.16
OpenSSL 1.1.1