Programming Tutorials

Sending emails using SMTP in Ruby

By: James Edward Gray II in Ruby Tutorials on 2009-03-03  

You must open a connection to an SMTP server before sending messages. The first argument is the address of your SMTP server, and the second argument is the port number. Using SMTP.start with a block is the simplest way to do this. This way, the SMTP connection is closed automatically after the block is executed.

    require 'net/smtp'
    Net::SMTP.start('your.smtp.server', 25) do |smtp|
      # Use the SMTP object smtp only in this block.
    end

Replace 'your.smtp.server" with your SMTP server. Normally your system manager or internet provider supplies a server for you.

Then you can send messages.

    msgstr = <<END_OF_MESSAGE
    From: Your Name <[email protected]>
    To: Destination Address <[email protected]>
    Subject: test message
    Date: Sat, 23 Jun 2001 16:26:43 +0900
    Message-Id: <[email protected]>

    This is a test message.
    END_OF_MESSAGE

    require 'net/smtp'
    Net::SMTP.start('your.smtp.server', 25) do |smtp|
      smtp.send_message msgstr,
                        '[email protected]',
                        '[email protected]'
    end

Closing the Session

You MUST close the SMTP session after sending messages, by calling the finish method:

    # using SMTP#finish
    smtp = Net::SMTP.start('your.smtp.server', 25)
    smtp.send_message msgstr, 'from@address', 'to@address'
    smtp.finish

You can also use the block form of SMTP.start/SMTP#start. This closes the SMTP session automatically:

    # using block form of SMTP.start
    Net::SMTP.start('your.smtp.server', 25) do |smtp|
      smtp.send_message msgstr, 'from@address', 'to@address'
    end

I strongly recommend this scheme. This form is simpler and more robust.

HELO domain

In almost all situations, you must provide a third argument to SMTP.start/SMTP#start. This is the domain name which you are on (the host to send mail from). It is called the "HELO domain". The SMTP server will judge whether it should send or reject the SMTP session by inspecting the HELO domain.

    Net::SMTP.start('your.smtp.server', 25,
                    'mail.from.domain') { |smtp| ... }

SMTP Authentication

The Net::SMTP class supports three authentication schemes; PLAIN, LOGIN and CRAM MD5. (SMTP Authentication: [RFC2554]) To use SMTP authentication, pass extra arguments to SMTP.start/SMTP#start.

    # PLAIN
    Net::SMTP.start('your.smtp.server', 25, 'mail.from.domain',
                    'Your Account', 'Your Password', :plain)
    # LOGIN
    Net::SMTP.start('your.smtp.server', 25, 'mail.from.domain',
                    'Your Account', 'Your Password', :login)

    # CRAM MD5
    Net::SMTP.start('your.smtp.server', 25, 'mail.from.domain',
                    'Your Account', 'Your Password', :cram_md5)