send email via telnet ruby script - ruby

Question

I'm new with ruby and need to send an email via telnet using a relay host with no authentication. I can do it with a linux shell but I need to put it in a script so I can "simplify" its use, I know it's not the best way but I can't find other since the server where i'm working on it's severely restricted and limited.
require 'net/telnet.rb'
mail = Net::Telnet::new(
"Host" => "domain.ip", # default: "localhost"
"Port" => 25, # default: 23
"Output_log" => "output_log", # default: nil (no output)
"Dump_log" => "dump_log", # default: nil (no output)
"Prompt" => /[$%#>] \z/n, # default: /[$%#>] \z/n
"Telnetmode" => true, # default: true
"Timeout" => 10, # default: 10
"Waittime" => 0, # default: 0
)
mail.cmd('helo MYDOMAIN'){ |c| print c }
mail.cmd('mail from: test#domain.com')
mail.cmd('rcpt to: test2#domain.com')
mail.cmd('data')
mail.cmd("subject: test cmd \n\n mensaje de prueba\n\n")
mail.cmd(".\n")
mail.close
I found the net/telnet.rb ruby class and this is my try... after mail.cmd('helo MYDOMAIN') I can't keep writing other commands, what I get is:
220 mail.server.com ESMTP
250 mail.server.com
After this I'm suposed to write mail from, etc. to create the mail. But I can't in the ruby script. I have try using:
mail.puts('mail from: test...')
mail.write('mail from: test...')
mail.print('mail from: test...')
mail.cmd('mail from: test...')
As written in documentation
Also I don't get the telnetmode(true|false) command maybe you could explain it to me please.
-- Edit --
Shell code trying to emulate:
telnet domain.ip 25
#=> Trying domain.ip...
#=> Connected to domain.ip.
#=> Escape character is '^]'.
#=> 220 mail.server.com ESMTP
helo MYDOMAIN
#=>250 mail.server.com
mail from:test#mydomain.com
#=> 250 2.1.0 Ok
rcpt to:test2#mydomain.com
#=> 250 2.1.0 Ok
data
#=> 354 End data with <CR><LF>.<CR><LF>
subject: test mail
test mail body
.
#=> 250 2.0.0 =k: queued as B6F08480D12
quit
#=> 221 2.0.0 Bye
#=> Connection closed by foreign host.

Answer 1

The telnet protocol is really, really rudimentary which is why the telnet command is useful for testing TCP/IP based services such as SMTP or HTTP. It does not mean those services actually use the telnet protocol, as they don't. They're conveniently plain-text in nature which means it's practical to use telnet for simple tests.
You should not be using the Telnet module for anything other than connecting to telnet services, though given it's 2017 it's unlikely you'll find any of those around.
You should be using something like Socket to connect. This can create a bare TCP/IP connection with full control over sending. As this is a wrapper around a regular POSIX filehandle you can use all the IO methods on it for reading, writing, and other control functions, like a proper socket shutdown.
Writing an SMTP adapter is not as easy as it seems, there's a lot of tricky things to tackle with regard to IO. You'll need to use IO.select to properly test for new data, plus that the socket is clear to write your email.
Here's a new stub:
require 'socket'
mail = TCPSocket.new("smtp.example.com", 25)
mail.write("HELO example.com\r\n")
Another note is that when you call require you should never specify the file extension. It's always handled for you.

Answer 2

Thanks to the help of the user ddubs how suggest the net\smtp gem (One that I didn't know) I was able to create a simple mail sender and using the mailfactory gem
Is it a strict requirement that you use telnet? Using ruby-doc.org/stdlib-2.0.0/libdoc/net/smtp/rdoc/Net/SMTP.html will turn your "difficult to maintain" script into something that is much easier to maintain. Even for someone who is completely new to Ruby. – ddubs
Here is the code sample
require 'net/smtp'
require 'mailfactory'
mail_body_HTML = '<h1> mail title</h1> your text in <b>HTML</b>'
mail_body_PLAIN = 'this is plain text'
mail_subject = 'test email'
mail_from = 'noreply#mydomain.com'
mail_to = 'user#otherdomain.com'
# mail_filePath = ''
mail = MailFactory.new()
mail.to = mail_to
mail.from = mail_from
mail.subject = mail_subject
mail.html = mail_body_HTML
# mail.text = mail_body_PLAIN
# mail.attach(mail_filePath)
relay_ip = x.x.x.x
Net::SMTP.start(relay_ip,25) do |smtp|
smtp.send_message(mail.to_s, mail_from, mail_to)
end