Capabilities of the "mail" gem, without ActionMailer (my presentation from our local Ruby meetups)

01.rb

require "mail"

Mail.defaults do
  delivery_method :smtp,
    address:        "smtp.gmail.com",
    port:           587,
    user_name:      ENV["GMAIL_EMAIL"],
    password:       ENV["GMAIL_PASSWORD"],
    authentication: "plain",
end

Mail.deliver do
  from    "janko.marohnic@gmail.com"
  to      "windows@microsoft.com"
  subject "Windows problem"

  text_part do
    body    <<-EMAIL
      Dear Microsoft,

      Could you please deprecate Windows?

      Sincerely,
      Janko
    EMAIL
  end

  html_part do
    content_type "text/html; charset=UTF-8"
    body    <<-EMAIL
      <p>Dear Microsoft,</p>

      <p>Could you please deprecate Windows?</p>

      <p>
        Sincerely,<br>
        Janko
      </p>
    EMAIL
  end
end

02.rb

require "mail"

email = Mail.new

email # => #<Mail::Message:70260121687560, Multipart: false, Headers: >
email["from"] = "janko.marohnic@gmail.com"
email[:to]    = "windows@microsoft.com"
email.subject = "The Windows Problem"

email.body    = <<-EMAIL
Hi Microsoft,

Could you please deprecate Windows?

Sincerely,
Janko
EMAIL

03.rb

require "mail"

email = Mail.new do
  from    "janko.marohnic@gmail.com"
  to      "windows@microsoft.com"
  subject "Windows problem"
  body    File.read("body.txt")

  add_file "/path/to/file.jpg"
  add_file filename: "image.png", content: content
end

04.rb

require "mail"

Mail.defaults do
  retriever_method :pop3,
    address:    "pop.gmail.com",
    port:       995,
    user_name:  'janko.marohnic@gmail.com',
    password:   "jncdbxqvqmkpkgbk",
    enable_ssl: true
end

puts Mail.find(count: 10, order: :desc).map(&:subject)

05.rb

require "mail"

mail = Mail.read("message.eml")

mail.from            # => ["d.tomaszova@gmail.com"]
mail.to              # => ["janko.marohnic@gmail.com"]
mail.subject         # => "Povrat poreza"
mail.date.to_s       # => "2015-01-28T22:32:28+01:00"
mail.message_id      # => "CAL_xHx=By+-Pnp-36siGn630P5wi56Q0BiEcxKLS8fESrctk_A@mail.gmail.com"
mail.body.decoded    # => "..."

06.rb

require "mail"

mail = Mail.read('/path/to/bounce_message.eml')

mail.bounced?         #=> true
mail.final_recipient  #=> rfc822;mikel@dont.exist.com
mail.action           #=> failed
mail.error_status     #=> 5.5.0
mail.diagnostic_code  #=> smtp;550 Requested action not taken: mailbox unavailable
mail.retryable?       #=> false

07.rb

require "mail"

Mail.defaults do
  delivery_method :test
end

Mail::TestMailer.deliveries