Update 'README.md'

README.md

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-# postman-rails
+# Postman for Rails
 
-A Rails library for the Postman email platform
+Postman for Rails allows you to integrate Postman directly into Action Mailer in a Rails application. There's no need to change any of your existing mailers, you just need to update your environment config.
+
+## Installation
+
+Add the `postman-rails` gem to your Gemfile and run `bundle install` to install it.
+
+```ruby
+gem 'postman-rails', '~> 1.0'
+```
+
+## Configuration
+
+Open up your `config/environment/production.rb` or `config/environment/development.rb` and change the delivery method to `postman`.
+
+```ruby
+config.action_mailer.delivery_method = :postman
+```
+
+You'll also need to provide your server key. If you don't have a server key, login to your web interface and generate a credential for the server you wish to send messages through.
+
+You also need to set the `POSTMAN_KEY` environment variable to include key and `POSTMAN_HOST` to include the hostname of your Postman service.
+
+Alternatively, you can configure it as shown below in your environment configuration file along with the `delivery_method`.
+
+```ruby
+config.action_mailer.postman_settings = {:host => "postman.prmail.vn", :server_key => "xxxxx"}
+```
+
+That's it! Send an email to test everything is working as you'd expect. Remember, if you have `raise_delivery_errors` set to false you might not see any errors. Use `deliver!` when running your tests so any exceptions are raised.
+
+Don't forget, you need to make sure that you're sending mail from domains that are added & verified to your Postman domain.