(Ruby) Send Email without Mail Server

How to send an email without a mail server (so-to-speak).

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

# Is it really possible to send email without connecting to
# a mail server?  Not really.

# When people ask 'Do you support sending email without 
# a mail server'?  what they're really asking is: 'I don't
# have an SMTP server, and I want to send email.  I see
# other components available where it's not necessary
# to specify an SMTP server.  Does your component have that
# ability?'  In short, the answer is Yes.  But you need
# to understand some things before you jump in...

# Here's what happens inside those other components
# that claim to not need a mail server:  The component does
# a DNS MX lookup using the intended recipient's email address
# to find the mail server (i.e. SMTP server) for that
# domain.  It then connects to that server and delivers the
# email.  You're still connecting to an SMTP server -- just
# not YOUR server.

# Chilkat provides an MxLookup method where you can lookup
# the SMTP hostname that services any given email address. 
# You would then assign the SmtpHost property to this value.
# Chilkat can then connect directly to the recipient's mail 
# server and deliver the email.

# There are a few gotcha's though...

# First, if you're writing an application that is widely 
# distributed, your app might be running within a network
# that blocks outgoing connections to the SMTP port.
# Earthlink, for example, is one major ISP that does this.
# When you are connected to the Internet via Earthlink,
# your apps can *only* connect to Earthlink's SMTP server
# and will not be able to reach any remote servers.  To send
# email, you must use Earthlink's SMTP as a relay.  This is
# common with ISPs.  So... if your application is coded
# as in this example, it will not work within those networks.
# 
# Second, some SMTP servers will reject unauthenticated
# sessions attempting to send email from dynamic IP addresses.
# You may see this error in your LastErrorText:
# 553-Your attempt to send email to us has been blocked
# 553-because your email server is not currently on that domain's Accepted
# 553-Senders list. To request addition to their Accepted Senders list,
# 553-please navigate with a Web browser to the following URL:
# 553-http://reportrbl.gate2service.com/Whitelist/?IPAddress=67.173.123.150
# 553 See http://www.dnsbl.us.sorbs.net/ (dul)

# In a nutshell, just because you were able to do the MxLookup
# and connect to the recipient's mail server, doesn't mean
# you'll be able to send email -- it depends on the IP address
# from which you're connecting.

# Finally, the DNS lookup is potentially time consuming.
# In addition, you cannot use somebody else's email server
# as a relay, so if you're connecting to smtp.xyz.com, you
# can only send email to email addresses at xyz.com.
# To send email to 3 recipients at different domains means
# making 3 separate connections to 3 separate SMTP servers
# to send the email one at a time.

# The mailman object is used for sending and receiving email.
mailman = Chilkat::CkMailMan.new()

recipient = "admin@chilkatsoft.com"

# Do a DNS MX lookup for the recipient's mail server.

smtpHostname = mailman.mxLookup(recipient)
if (mailman.get_LastMethodSuccess() != true)
    print mailman.lastErrorText() + "\n";
    exit
end

print smtpHostname + "\n";

# Set the SMTP server.
mailman.put_SmtpHost(smtpHostname)

# Create a new email object
email = Chilkat::CkEmail.new()

email.put_Subject("This is a test")
email.put_Body("This is a test")
email.put_From("My Name <myname@mydomain.com>")
email.AddTo("",recipient)

success = mailman.SendEmail(email)
if (success != true)
    print mailman.lastErrorText() + "\n";
else
    print "Mail Sent!" + "\n";
end