diff --git a/config/environments/production.rb b/config/environments/production.rb
index 63270ae..19fefdf 100644
--- a/config/environments/production.rb
+++ b/config/environments/production.rb
@@ -63,12 +63,12 @@
   # Set this to true and configure the email server for immediate delivery to raise delivery errors.
   # config.action_mailer.raise_delivery_errors = false
 
-  # Send mail through SES (see app/lib/ses_delivery_method.rb and
-  # config/initializers/action_mailer_ses.rb), authenticating via the instance/task's
-  # IAM role through the AWS SDK's standard credential chain - no explicit AWS
-  # credentials configured here.
+  # Send mail through SES. Registration (and the region setting) lives in
+  # config/initializers/action_mailer_ses.rb / app/lib/ses_delivery_method.rb, not
+  # here - see the comment there for why. Authenticates via the instance/task's IAM
+  # role through the AWS SDK's standard credential chain, no explicit AWS credentials
+  # configured here.
   config.action_mailer.delivery_method = :ses
-  config.action_mailer.ses_settings = { region: ENV.fetch('AWS_REGION', 'us-east-1') }
 
   # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
   # the I18n.default_locale when a translation cannot be found).
diff --git a/config/initializers/action_mailer_ses.rb b/config/initializers/action_mailer_ses.rb
index 81bed49..78968a6 100644
--- a/config/initializers/action_mailer_ses.rb
+++ b/config/initializers/action_mailer_ses.rb
@@ -4,4 +4,10 @@
 # before Zeitwerk has the app/lib root set up.
 require Rails.root.join('app/lib/ses_delivery_method')
 
-ActionMailer::Base.add_delivery_method :ses, SesDeliveryMethod
+# Passed here, as add_delivery_method's default_options, rather than via
+# config.action_mailer.ses_settings in config/environments/*.rb: referencing
+# ActionMailer::Base below is what triggers its first load in this app, and Rails
+# applies config.action_mailer.* settings via a load hook that fires on that same
+# first load - so a `ses_settings=` assigned in production.rb would run before this
+# add_delivery_method call has defined that setter, raising NoMethodError.
+ActionMailer::Base.add_delivery_method :ses, SesDeliveryMethod, region: ENV.fetch('AWS_REGION', 'us-east-1')