GitLab outgoing email stopped working when we upgraded from 19.0.1 to 19.0.2. Since 2018 our gitlab.rb was configured as such: ``` ... gitlab_rails['smtp_authentication'] = false ... ``` With the same configuration file, attempting to send an email through console failed as follows: ``` $ sudo gitlab-rails console -------------------------------------------------------------------------------- Ruby: ruby 3.3.11 (2026-03-26 revision 1f2d15125a) [x86_64-linux] GitLab: 19.0.2-ee (86c99d562e4) EE GitLab Shell: 14.51.0 PostgreSQL: 17.8 ------------------------------------------------------------[ booted in 30.35s ] Loading production environment (Rails 7.2.3.1) gitlab(prod)> Notify.test_email('whatever@gmail.com', 'Hello World', 'This is a test message').deliver_now net-smtp (0.5.1) lib/net/smtp.rb:883:in `check_auth_args': wrong authentication type false (ArgumentError) raise ArgumentError, "wrong authentication type #{type}" ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ from net-smtp (0.5.1) lib/net/smtp.rb:669:in `do_start' from net-smtp (0.5.1) lib/net/smtp.rb:642:in `start' from config/initializers/mail_starttls_patch.rb:53:in `start_smtp_session' from mail (2.9.0) lib/mail/network/delivery_methods/smtp.rb:108:in `deliver!' from mail (2.9.0) lib/mail/message.rb:2148:in `do_delivery' from mail (2.9.0) lib/mail/message.rb:253:in `block in deliver' from actionmailer (7.2.3.1) lib/action_mailer/base.rb:595:in `block in deliver_mail' from activesupport (7.2.3.1) lib/active_support/notifications.rb:212:in `instrument' from actionmailer (7.2.3.1) lib/action_mailer/base.rb:593:in `deliver_mail' from mail (2.9.0) lib/mail/message.rb:253:in `deliver' from actionmailer (7.2.3.1) lib/action_mailer/message_delivery.rb:126:in `block (2 levels) in deliver_now' from activesupport (7.2.3.1) lib/active_support/callbacks.rb:101:in `run_callbacks' from actionmailer (7.2.3.1) lib/action_mailer/message_delivery.rb:125:in `block in deliver_now' from actionmailer (7.2.3.1) lib/action_mailer/rescuable.rb:21:in `handle_exceptions' from actionmailer (7.2.3.1) lib/action_mailer/message_delivery.rb:124:in `deliver_now' from (gitlab):3:in `<main>' ... 17 levels... ``` Removing `gitlab_rails['smtp_authentication'] = false` from gitlab.rb, reconfiguring gitlab, and attempting to send the email again, works. ``` $ sudo sed -i '/smtp_authentication/d' /etc/gitlab/gitlab.rb $ sudo gitlab-ctl reconfigure $ sudo gitlab-rails console -------------------------------------------------------------------------------- Ruby: ruby 3.3.11 (2026-03-26 revision 1f2d15125a) [x86_64-linux] GitLab: 19.0.2-ee (86c99d562e4) EE GitLab Shell: 14.51.0 PostgreSQL: 17.8 ------------------------------------------------------------[ booted in 34.59s ] Loading production environment (Rails 7.2.3.1) gitlab(prod)> Notify.test_email('whatever@gmail.com', 'Message Subject', 'Message Body').deliver_now => #<Mail::Message:1637460, Multipart: false, Headers: <Date: Wed, 17 Jun 2026 13:35:59 +0000>, <Subject: Message Subject>, <MIME-Version: 1.0>, <Content-Type: text/html; charset=UTF-8>, <Content-Transfer-Encoding: 7bit>, <Auto-Submitted: auto-generated>, <X-Auto-Response-Suppress: All>> gitlab(prod)> ``` (part of the <Mail::> output redacted for privacy). We noticed that GitLab 19.0.2 bumped the net-smtp library: ``` $ git diff v19.0.1-ee..v19.0.2-ee ... - net-smtp (0.3.3) + net-smtp (0.5.1) ... ``` Possibly the issue was introduced in https://github.com/ruby/net-smtp/pull/73/changes, though I'm not familiar enough with Ruby to tell for certain.