action_mailbox_example.rb

COMMENTS_REGEX = /^comment\+(.+)@example\.com/i

# app/mailboxes/application_mailbox.rb
class ApplicationMailbox < ActionMailbox::Base
  routing COMMENTS_REGEX => :comments
end

# app/mailboxes/comments_mailbox.rb
class CommentsMailbox < ApplicationMailbox
  def process
    user = User.find_by(email: mail.from)
    post_uuid = COMMENTS_REGEX.match(mail.to)[1]
    
    post = Post.find_by(uuid: post_uuid)
    post.comments.create(user: user, content: mail.body)
  end
end