sending the simplest of emails? (ruby or RoR)

(newbe)
Am I missing something very basic, what does it take for me to send a simple email with 'hello' to my personal inbox in ruby (or Rails)
in php it's this simple : mail("someone@example.com","My subject",$msg);

I know php has to be running from a server to able to do anything, but what would I need to get the equivalent in ruby (or rails?) from my local computer?

I tried the Rails Guides Action mailer basics only to be rewarded with output in the terminal :(

...or copy and paste the following from https://www.tutorialspoint.com/ruby/ruby_sending_email.htm
with the following code running in a test_email.rb file and execute with $ruby test_email.rb

require 'net/smtp'

message = < From: Private Person
To: A Test User
Subject: SMTP e-mail test

This is a test e-mail message.
MESSAGE_END

Net::SMTP.start('localhost') do |smtp|
smtp.send_message message, 'me@fromdomain.com', 'my_personal_email_here@me.com'
end

Returns this :
/Users/me/.rbenv/versions/2.7.2/lib/ruby/2.7.0/net/smtp.rb:539:in `initialize': Connection refused - connect(2) for "localhost" port 25 (Errno::ECONNREFUSED)

(Can that only run from a server?)

It's looking for an SMTP server running on your machine on port 25. You'd have to run something like postfix to do that.