rails new

THOR_MERGE=vimdiff bundle exec rails new -d mysql --skip-action-mailbox
  --skip-action-text --skip-active-job --skip-active-storage
  --skip-action-cable --skip-hotwire --skip-jbuilder --skip-bootsnap
  --skip-bundle .

app/mailers/application_mailer.rb

@@ -0,0 +1,4 @@
+class ApplicationMailer < ActionMailer::Base
+  default from: "from@example.com"
+  layout "mailer"
+end