Rails 5.1.0.rc1 (March 20, 2017)

Rails 5.1.0.beta1 (February 23, 2017)

Add :args to process.action_mailer event.

Yuji Yaginuma
Add parameterized invocation of mailers as a way to share before filters and defaults between actions. See ActionMailer::Parameterized for a full example of the benefit.

DHH
Allow lambdas to be used as lazy defaults in addition to procs.

DHH

Mime type: allow to custom content type when setting body in headers and attachments.

Example:

def test_emails
  attachments["invoice.pdf"] = "This is test File content"
  mail(body: "Hello there", content_type: "text/html")
end

Minh Quy

Exception handling: use rescue_from to handle exceptions raised by mailer actions, by message delivery, and by deferred delivery jobs.

Jeremy Daer

Please check 5-0-stable for previous changes.