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Net::SMTP

What is This Library? ↑

This library provides functionality to send internet mail via SMTP, the Simple Mail Transfer Protocol. For details of SMTP itself, see [RFC2821] (www.ietf.org/rfc/rfc2821.txt).

What is This Library NOT? ↑

This library does NOT provide functions to compose internet mails. You must create them by yourself. If you want better mail support, try RubyMail or TMail or search for alternatives in RubyGems.org or The Ruby Toolbox.

FYI: the official documentation on internet mail is: [RFC2822] (www.ietf.org/rfc/rfc2822.txt).

Examples ↑

Sending Messages ↑

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 <your@mail.address>
To: Destination Address <someone@example.com>
Subject: test message
Date: Sat, 23 Jun 2001 16:26:43 +0900
Message-Id: <unique.message.id.string@example.com>

This is a test message.
END_OF_MESSAGE

require 'net/smtp'
Net::SMTP.start('your.smtp.server', 25) do |smtp|
  smtp.send_message msgstr,
                    'your@mail.address',
                    'his_address@example.com'
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
                helo: '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
                user: 'Your Account', secret: 'Your Password', authtype: :plain)
# LOGIN
Net::SMTP.start('your.smtp.server', 25
                user: 'Your Account', secret: 'Your Password', authtype: :login)

# CRAM MD5
Net::SMTP.start('your.smtp.server', 25
                user: 'Your Account', secret: 'Your Password', authtype: :cram_md5)

Attributes

address[R]

The address of the SMTP server to connect to.

esmtp[RW]

Set whether to use ESMTP or not. This should be done before calling start. Note that if start is called in ESMTP mode, and the connection fails due to a ProtocolError, the SMTP object will automatically switch to plain SMTP mode and retry (but not vice versa).

esmtp?[RW]

Set whether to use ESMTP or not. This should be done before calling start. Note that if start is called in ESMTP mode, and the connection fails due to a ProtocolError, the SMTP object will automatically switch to plain SMTP mode and retry (but not vice versa).

open_timeout[RW]

Seconds to wait while attempting to open a connection. If the connection cannot be opened within this time, a Net::OpenTimeout is raised. The default value is 30 seconds.

port[R]

The port number of the SMTP server to connect to.

read_timeout[R]

Seconds to wait while reading one block (by one read(2) call). If the read(2) call does not complete within this time, a Net::ReadTimeout is raised. The default value is 60 seconds.

Public Class Methods

default_port() click to toggle source

The default SMTP port number, 25.

 
               # File net/smtp.rb, line 176
def SMTP.default_port
  25
end
default_ssl_context(verify_peer=true) click to toggle source 
 
               # File net/smtp.rb, line 194
def SMTP.default_ssl_context(verify_peer=true)
  context = OpenSSL::SSL::SSLContext.new
  context.verify_mode = verify_peer ? OpenSSL::SSL::VERIFY_PEER : OpenSSL::SSL::VERIFY_NONE
  store = OpenSSL::X509::Store.new
  store.set_default_paths
  context.cert_store = store
  context
end
default_ssl_port() click to toggle source
Alias for: default_tls_port
default_submission_port() click to toggle source

The default mail submission port number, 587.

 
               # File net/smtp.rb, line 181
def SMTP.default_submission_port
  587
end
default_tls_port() click to toggle source

The default SMTPS port number, 465.

 
               # File net/smtp.rb, line 186
def SMTP.default_tls_port
  465
end
Also aliased as: default_ssl_port
new(address, port = nil) click to toggle source

Creates a new Net::SMTP object.

address is the hostname or ip address of your SMTP server. port is the port to connect to; it defaults to port 25.

This method does not open the TCP connection. You can use SMTP.start instead of SMTP.new if you want to do everything at once. Otherwise, follow SMTP.new with SMTP#start.

 
               # File net/smtp.rb, line 214
def initialize(address, port = nil)
  @address = address
  @port = (port || SMTP.default_port)
  @esmtp = true
  @capabilities = nil
  @socket = nil
  @started = false
  @open_timeout = 30
  @read_timeout = 60
  @error_occurred = false
  @debug_output = nil
  @tls = false
  @starttls = :auto
  @ssl_context_tls = nil
  @ssl_context_starttls = nil
end
start(address, port = nil, helo: 'localhost', user: nil, secret: nil, authtype: nil, tls_verify: true, tls_hostname: nil) { |smtp| ... } click to toggle source
start(address, port = nil, helo = 'localhost', user = nil, secret = nil, authtype = nil) { |smtp| ... }

Creates a new Net::SMTP object and connects to the server.

This method is equivalent to:

Net::SMTP.new(address, port).start(helo: helo_domain, user: account, secret: password, authtype: authtype, tls_verify: flag, tls_hostname: hostname)

Example ↑

Net::SMTP.start('your.smtp.server') do |smtp|
  smtp.send_message msgstr, 'from@example.com', ['dest@example.com']
end

Block Usage ↑

If called with a block, the newly-opened Net::SMTP object is yielded to the block, and automatically closed when the block finishes. If called without a block, the newly-opened Net::SMTP object is returned to the caller, and it is the caller's responsibility to close it when finished.

Parameters ↑

address is the hostname or ip address of your smtp server.

port is the port to connect to; it defaults to port 25.

helo is the HELO domain provided by the client to the server (see overview comments); it defaults to 'localhost'.

The remaining arguments are used for SMTP authentication, if required or desired. user is the account name; secret is your password or other authentication token; and authtype is the authentication type, one of :plain, :login, or :cram_md5. See the discussion of SMTP Authentication in the overview notes. If tls_verify is true, verify the server's certificate. The default is true. If the hostname in the server certificate is different from address, it can be specified with tls_hostname.

Errors ↑

This method may raise:

 
               # File net/smtp.rb, line 466
def SMTP.start(address, port = nil, *args, helo: nil,
               user: nil, secret: nil, password: nil, authtype: nil,
               tls_verify: true, tls_hostname: nil,
               &block)
  raise ArgumentError, "wrong number of arguments (given #{args.size + 2}, expected 1..6)" if args.size > 4
  helo ||= args[0] || 'localhost'
  user ||= args[1]
  secret ||= password || args[2]
  authtype ||= args[3]
  new(address, port).start(helo: helo, user: user, secret: secret, authtype: authtype, tls_verify: tls_verify, tls_hostname: tls_hostname, &block)
end

Public Instance Methods

auth_cram_md5(user, secret) click to toggle source 
 
               # File net/smtp.rb, line 791
def auth_cram_md5(user, secret)
  check_auth_args user, secret
  res = critical {
    res0 = get_response('AUTH CRAM-MD5')
    check_auth_continue res0
    crammed = cram_md5_response(secret, res0.cram_md5_challenge)
    get_response(base64_encode("#{user} #{crammed}"))
  }
  check_auth_response res
  res
end
auth_login(user, secret) click to toggle source 
 
               # File net/smtp.rb, line 780
def auth_login(user, secret)
  check_auth_args user, secret
  res = critical {
    check_auth_continue get_response('AUTH LOGIN')
    check_auth_continue get_response(base64_encode(user))
    get_response(base64_encode(secret))
  }
  check_auth_response res
  res
end
auth_plain(user, secret) click to toggle source 
 
               # File net/smtp.rb, line 771
def auth_plain(user, secret)
  check_auth_args user, secret
  res = critical {
    get_response('AUTH PLAIN ' + base64_encode("\0#{user}\0#{secret}"))
  }
  check_auth_response res
  res
end
authenticate(user, secret, authtype = DEFAULT_AUTH_TYPE) click to toggle source 
 
               # File net/smtp.rb, line 765
def authenticate(user, secret, authtype = DEFAULT_AUTH_TYPE)
  check_auth_method authtype
  check_auth_args user, secret
  public_send auth_method(authtype), user, secret
end
capable_auth_types() click to toggle source

Returns supported authentication methods on this server. You cannot get valid value before opening SMTP session.

 
               # File net/smtp.rb, line 287
def capable_auth_types
  return [] unless @capabilities
  return [] unless @capabilities['AUTH']
  @capabilities['AUTH']
end
capable_cram_md5_auth?() click to toggle source

true if server advertises AUTH CRAM-MD5. You cannot get valid value before opening SMTP session.

 
               # File net/smtp.rb, line 274
def capable_cram_md5_auth?
  auth_capable?('CRAM-MD5')
end
capable_login_auth?() click to toggle source

true if server advertises AUTH LOGIN. You cannot get valid value before opening SMTP session.

 
               # File net/smtp.rb, line 268
def capable_login_auth?
  auth_capable?('LOGIN')
end
capable_plain_auth?() click to toggle source

true if server advertises AUTH PLAIN. You cannot get valid value before opening SMTP session.

 
               # File net/smtp.rb, line 262
def capable_plain_auth?
  auth_capable?('PLAIN')
end
capable_starttls?() click to toggle source

true if server advertises STARTTLS. You cannot get valid value before opening SMTP session.

 
               # File net/smtp.rb, line 250
def capable_starttls?
  capable?('STARTTLS')
end
data(msgstr = nil) click to toggle source

This method sends a message. If msgstr is given, sends it as a message. If block is given, yield a message writer stream. You must write message before the block is closed.

# Example 1 (by string)
smtp.data(<<EndMessage)
From: john@example.com
To: betty@example.com
Subject: I found a bug

Check vm.c:58879.
EndMessage

# Example 2 (by block)
smtp.data {|f|
  f.puts "From: john@example.com"
  f.puts "To: betty@example.com"
  f.puts "Subject: I found a bug"
  f.puts ""
  f.puts "Check vm.c:58879."
}

 
               # File net/smtp.rb, line 925
def data(msgstr = nil, &block)   #:yield: stream
  if msgstr and block
    raise ArgumentError, "message and block are exclusive"
  end
  unless msgstr or block
    raise ArgumentError, "message or block is required"
  end
  res = critical {
    check_continue get_response('DATA')
    socket_sync_bak = @socket.io.sync
    begin
      @socket.io.sync = false
      if msgstr
        @socket.write_message msgstr
      else
        @socket.write_message_by_block(&block)
      end
    ensure
      @socket.io.flush
      @socket.io.sync = socket_sync_bak
    end
    recv_response()
  }
  check_response res
  res
end
debug_output=(arg) click to toggle source

WARNING: This method causes serious security holes. Use this method for only debugging.

Set an output stream for debug logging. You must call this before start.

# example
smtp = Net::SMTP.new(addr, port)
smtp.set_debug_output $stderr
smtp.start do |smtp|
  ....
end
 
               # File net/smtp.rb, line 400
def debug_output=(arg)
  @debug_output = arg
end
Also aliased as: set_debug_output
disable_ssl() click to toggle source
Alias for: disable_tls
disable_starttls() click to toggle source

Disables SMTP/TLS (STARTTLS) for this object. Must be called before the connection is established to have any effect.

 
               # File net/smtp.rb, line 358
def disable_starttls
  @starttls = false
  @ssl_context_starttls = nil
end
disable_tls() click to toggle source

Disables SMTP/TLS for this object. Must be called before the connection is established to have any effect.

 
               # File net/smtp.rb, line 314
def disable_tls
  @tls = false
  @ssl_context_tls = nil
end
Also aliased as: disable_ssl
ehlo(domain) click to toggle source 
 
               # File net/smtp.rb, line 869
def ehlo(domain)
  getok("EHLO #{domain}")
end
enable_ssl(context = nil) click to toggle source
Alias for: enable_tls
enable_starttls(context = nil) click to toggle source

Enables SMTP/TLS (STARTTLS) for this object. context is a OpenSSL::SSL::SSLContext object.

 
               # File net/smtp.rb, line 340
def enable_starttls(context = nil)
  raise 'openssl library not installed' unless defined?(OpenSSL)
  raise ArgumentError, "SMTPS and STARTTLS is exclusive" if @tls
  @starttls = :always
  @ssl_context_starttls = context
end
enable_starttls_auto(context = nil) click to toggle source

Enables SMTP/TLS (STARTTLS) for this object if server accepts. context is a OpenSSL::SSL::SSLContext object.

 
               # File net/smtp.rb, line 349
def enable_starttls_auto(context = nil)
  raise 'openssl library not installed' unless defined?(OpenSSL)
  raise ArgumentError, "SMTPS and STARTTLS is exclusive" if @tls
  @starttls = :auto
  @ssl_context_starttls = context
end
enable_tls(context = nil) click to toggle source

Enables SMTP/TLS (SMTPS: SMTP over direct TLS connection) for this object. Must be called before the connection is established to have any effect. context is a OpenSSL::SSL::SSLContext object.

 
               # File net/smtp.rb, line 303
def enable_tls(context = nil)
  raise 'openssl library not installed' unless defined?(OpenSSL)
  raise ArgumentError, "SMTPS and STARTTLS is exclusive" if @starttls == :always
  @tls = true
  @ssl_context_tls = context
end
Also aliased as: enable_ssl
finish() click to toggle source

Finishes the SMTP session and closes TCP connection. Raises IOError if not started.

 
               # File net/smtp.rb, line 570
def finish
  raise IOError, 'not yet started' unless started?
  do_finish
end
helo(domain) click to toggle source 
 
               # File net/smtp.rb, line 865
def helo(domain)
  getok("HELO #{domain}")
end
inspect() click to toggle source

Provide human-readable stringification of class state.

 
               # File net/smtp.rb, line 232
def inspect
  "#<#{self.class} #{@address}:#{@port} started=#{@started}>"
end
mailfrom(from_addr) click to toggle source 
 
               # File net/smtp.rb, line 873
def mailfrom(from_addr)
  getok("MAIL FROM:<#{from_addr}>")
end
open_message_stream(from_addr, *to_addrs) click to toggle source

Opens a message writer stream and gives it to the block. The stream is valid only in the block, and has these methods:

puts(str = '')

outputs STR and CR LF.

print(str)

outputs STR.

printf(fmt, *args)

outputs sprintf(fmt,*args).

write(str)

outputs STR and returns the length of written bytes.

<<(str)

outputs STR and returns self.

If a single CR (“r”) or LF (“n”) is found in the message, it is converted to the CR LF pair. You cannot send a binary message with this method.

Parameters ↑

from_addr is a String representing the source mail address.

to_addr is a String or Strings or Array of Strings, representing the destination mail address or addresses.

Example ↑

Net::SMTP.start('smtp.example.com', 25) do |smtp|
  smtp.open_message_stream('from@example.com', ['dest@example.com']) do |f|
    f.puts 'From: from@example.com'
    f.puts 'To: dest@example.com'
    f.puts 'Subject: test message'
    f.puts
    f.puts 'This is a test message.'
  end
end

Errors ↑

This method may raise:

 
               # File net/smtp.rb, line 749
def open_message_stream(from_addr, *to_addrs, &block)   # :yield: stream
  raise IOError, 'closed session' unless @socket
  mailfrom from_addr
  rcptto_list(to_addrs) {data(&block)}
end
Also aliased as: ready
quit() click to toggle source 
 
               # File net/smtp.rb, line 952
def quit
  getok('QUIT')
end
rcptto(to_addr) click to toggle source 
 
               # File net/smtp.rb, line 898
def rcptto(to_addr)
  getok("RCPT TO:<#{to_addr}>")
end
rcptto_list(to_addrs) click to toggle source 
 
               # File net/smtp.rb, line 877
def rcptto_list(to_addrs)
  raise ArgumentError, 'mail destination not given' if to_addrs.empty?
  ok_users = []
  unknown_users = []
  to_addrs.flatten.each do |addr|
    begin
      rcptto addr
    rescue SMTPAuthenticationError
      unknown_users << addr.dump
    else
      ok_users << addr
    end
  end
  raise ArgumentError, 'mail destination not given' if ok_users.empty?
  ret = yield
  unless unknown_users.empty?
    raise SMTPAuthenticationError, "failed to deliver for #{unknown_users.join(', ')}"
  end
  ret
end
read_timeout=(sec) click to toggle source

Set the number of seconds to wait until timing-out a read(2) call.

 
               # File net/smtp.rb, line 381
def read_timeout=(sec)
  @socket.read_timeout = sec if @socket
  @read_timeout = sec
end
ready(from_addr, *to_addrs) click to toggle source
Alias for: open_message_stream
rset() click to toggle source

Aborts the current mail transaction

 
               # File net/smtp.rb, line 857
def rset
  getok('RSET')
end
send_mail(msgstr, from_addr, *to_addrs) click to toggle source
Alias for: send_message
send_message(msgstr, from_addr, *to_addrs) click to toggle source

Sends msgstr as a message. Single CR (“r”) and LF (“n”) found in the msgstr, are converted into the CR LF pair. You cannot send a binary message with this method. msgstr should include both the message headers and body.

from_addr is a String representing the source mail address.

to_addr is a String or Strings or Array of Strings, representing the destination mail address or addresses.

Example ↑

Net::SMTP.start('smtp.example.com') do |smtp|
  smtp.send_message msgstr,
                    'from@example.com',
                    ['dest@example.com', 'dest2@example.com']
end

Errors ↑

This method may raise:

 
               # File net/smtp.rb, line 696
def send_message(msgstr, from_addr, *to_addrs)
  raise IOError, 'closed session' unless @socket
  mailfrom from_addr
  rcptto_list(to_addrs) {data msgstr}
end
Also aliased as: send_mail, sendmail
sendmail(msgstr, from_addr, *to_addrs) click to toggle source
Alias for: send_message
set_debug_output(arg) click to toggle source
Alias for: debug_output=
ssl?() click to toggle source
Alias for: tls?
start(helo: 'localhost', user: nil, secret: nil, authtype: nil, tls_verify: true, tls_hostname: nil) { |smtp| ... } click to toggle source
start(helo = 'localhost', user = nil, secret = nil, authtype = nil) { |smtp| ... }

Opens a TCP connection and starts the SMTP session.

Parameters ↑

helo is the HELO domain that you'll dispatch mails from; see the discussion in the overview notes.

If both of user and secret are given, SMTP authentication will be attempted using the AUTH command. authtype specifies the type of authentication to attempt; it must be one of :login, :plain, and :cram_md5. See the notes on SMTP Authentication in the overview. If tls_verify is true, verify the server's certificate. The default is true. If the hostname in the server certificate is different from address, it can be specified with tls_hostname.

Block Usage ↑

When this methods is called with a block, the newly-started SMTP object is yielded to the block, and automatically closed after the block call finishes. Otherwise, it is the caller's responsibility to close the session when finished.

Example ↑

This is very similar to the class method SMTP.start.

require 'net/smtp'
smtp = Net::SMTP.new('smtp.mail.server', 25)
smtp.start(helo: helo_domain, user: account, secret: password, authtype: authtype) do |smtp|
  smtp.send_message msgstr, 'from@example.com', ['dest@example.com']
end

The primary use of this method (as opposed to SMTP.start) is probably to set debugging (set_debug_output) or ESMTP (esmtp=), which must be done before the session is started.

Errors ↑

If session has already been started, an IOError will be raised.

This method may raise:

 
               # File net/smtp.rb, line 541
def start(*args, helo: nil,
          user: nil, secret: nil, password: nil, authtype: nil, tls_verify: true, tls_hostname: nil)
  raise ArgumentError, "wrong number of arguments (given #{args.size}, expected 0..4)" if args.size > 4
  helo ||= args[0] || 'localhost'
  user ||= args[1]
  secret ||= password || args[2]
  authtype ||= args[3]
  if @tls && @ssl_context_tls.nil?
    @ssl_context_tls = SMTP.default_ssl_context(tls_verify)
  end
  if @starttls && @ssl_context_starttls.nil?
    @ssl_context_starttls = SMTP.default_ssl_context(tls_verify)
  end
  @tls_hostname = tls_hostname
  if block_given?
    begin
      do_start helo, user, secret, authtype
      return yield(self)
    ensure
      do_finish
    end
  else
    do_start helo, user, secret, authtype
    return self
  end
end
started?() click to toggle source

true if the SMTP session has been started.

 
               # File net/smtp.rb, line 479
def started?
  @started
end
starttls() click to toggle source 
 
               # File net/smtp.rb, line 861
def starttls
  getok('STARTTLS')
end
starttls?() click to toggle source

Returns truth value if this object uses STARTTLS. If this object always uses STARTTLS, returns :always. If this object uses STARTTLS when the server support TLS, returns :auto.

 
               # File net/smtp.rb, line 324
def starttls?
  @starttls
end
starttls_always?() click to toggle source

true if this object uses STARTTLS.

 
               # File net/smtp.rb, line 329
def starttls_always?
  @starttls == :always
end
starttls_auto?() click to toggle source

true if this object uses STARTTLS when server advertises STARTTLS.

 
               # File net/smtp.rb, line 334
def starttls_auto?
  @starttls == :auto
end
tls?() click to toggle source

true if this object uses SMTP/TLS (SMTPS).

 
               # File net/smtp.rb, line 294
def tls?
  @tls
end
Also aliased as: ssl?
There is an updated format of the API docs for this version here.