Fix SMTP configuration with mail 2.9.0 (#36646)

lib/mastodon/email_configuration_helper.rb

@@ -8,25 +8,23 @@ module Mastodon
     # `config/email.yml`) into the format that `ActionMailer` understands
     def convert_smtp_settings(config)
       enable_starttls = nil
-      enable_starttls_auto = nil
 
       case config[:enable_starttls]
       when 'always'
-        enable_starttls = true
-      when 'never'
+        enable_starttls = :always
+      when 'never', 'false'
         enable_starttls = false
       when 'auto'
-        enable_starttls_auto = true
+        enable_starttls = :auto
       else
-        enable_starttls_auto = config[:enable_starttls_auto] != 'false'
+        enable_starttls = config[:enable_starttls_auto] ? :auto : false unless config[:tls] || config[:ssl]
       end
 
       authentication = config[:authentication] == 'none' ? nil : (config[:authentication] || 'plain')
 
-      config.merge(
+      config.without(:enable_starttls_auto).merge(
         authentication:,
-        enable_starttls:,
-        enable_starttls_auto:
+        enable_starttls:
       )
     end
   end