Steps to reproduce the problem

1. Try to reset a password or confirm an e-mail from some new account
2. The message says the e-mail was sucessfully sent
3. The e-mail never reaches the SMTP server nor the user inbox
4. The Sidekiq mailers queue shows an error: ArgumentError: :enable_starttls and :tls are mutually exclusive

Expected behaviour

The e-mail is sent sucessfully

Actual behaviour

The e-mail never reaches its destination

Detailed description

Today I noticed that the instance wasn't sending e-mails. The service used (Scaleway TEM) didn't receive one single message since two days ago. A new user signed up, and they said the confirmation e-mail never arrived. I tried to reset my password just to test and the e-mail also was nowhere to be found.

E-mail configuration (.env.production):

# mail delivery
SMTP_SERVER=smtp.tem.scw.cloud
SMTP_SSL=true
SMTP_PORT=465
SMTP_LOGIN=ABCXYZ
SMTP_PASSWORD=ABCXYZ
SMTP_DELIVERY_METHOD=smtp
SMTP_FROM_ADDRESS='Bolhinha <[email protected]>'

Sidekiq error for e-mail deliveries (password reset, e-mail address change and e-mail address confirmation):

:enable_starttls and :tls are mutually exclusive. Set :tls if you're on an SMTPS connection. Set :enable_starttls if you're on an SMTP connection and using STARTTLS for secure TLS upgrade.

Mastodon instance

bolha.one, ursal.zone

Mastodon version

4.5.0-rc.1@2a9c7d2+bolhinha

Technical details

If this is happening on your own Mastodon server, please fill out those:

• Ruby version: ruby 3.4.7 (2025-10-08 revision 7a5688e2a2) +PRISM [x86_64-linux]
• Node.js version: v24.10.0