rails--rails/actionmailer/CHANGELOG.md

• Support the use of underscored symbols when registering interceptors and observers like we do elsewhere within Rails.

  Andrew White

• Add the ability to intercept emails before previewing in a similar fashion to how emails can be intercepted before delivery, e.g:

  class CSSInlineStyler
    def self.previewing_email(message)
      # inline CSS styles
    end
  end
  
  ActionMailer::Base.register_preview_interceptor CSSInlineStyler
  

  Fixes #13622.

  Andrew White

• Add mailer previews feature based on 37 Signals mail_view gem

  Andrew White

• Calling mail() without arguments serves as getter for the current mail message and keeps previously set headers.

  Fixes #13090.

  Example:

  class MailerWithCallback < ActionMailer::Base
    after_action :a_callback
  
    def welcome
      mail subject: "subject", to: ["joe@example.com"]
    end
  
    def a_callback
      mail # => returns the current mail message
    end
  end
  

  Yves Senn

• Instrument the generation of Action Mailer messages. The time it takes to generate a message is written to the log.

  Daniel Schierbeck

• Invoke mailer defaults as procs only if they are procs, do not convert with to_proc. That an object is convertible to a proc does not mean it's meant to be always used as a proc.

  Fixes #11533.

  Alex Tsukernik

Please check 4-0-stable for previous changes.