Added documentation for the reply-by-email to comment feature

README.md

@@ -80,12 +80,28 @@ Secure connection is needed for OAuth authentication etc.
 5. To see the installed list of cron jobs use command `crontab -l`
 6. For more details about this gem, visit the official repository of whenever gem.
 
+***
+
 ### Bundle exec
 
 For some, it will be necessary to prepend your gem-related commands with `bundle exec`, for example, `bundle exec passenger start`; adding `bundle exec` ensures you're using the version of passenger you just installed with Bundler. `bundle exec rake db: setup`, `bundle exec rake db: seed` are other examples of where this might be necessary.
 
 ***
 
+## How to start reply by email to comment feature
+
+With the merge of [fad88fd72c9d08f5591bf4c0cab402160eb9ea54](https://github.com/publiclab/plots2/commit/fad88fd72c9d08f5591bf4c0cab402160eb9ea54) Public lab now supports Reply-by-email to comment features to the various nodes. For implementing this feature we have used `mailman` gem which is a microframework for processing incoming email. More details about this can be found at [mailman](https://github.com/mailman/mailman).
+
+[This](https://github.com/publiclab/plots2/blob/master/script/mailman_server) file contains the script for starting the mailman server. It is using POP3 (Post Office Protocol version 3) to receive emails from a remote server to a local email client. All the configrations regarding this is to be done in [mailman script](https://github.com/publiclab/plots2/blob/master/script/mailman_server). 
+
+After configurations are done we are good to start the `mailman` server. For starting the server use the command `script/mailman` from the root directory of the project.
+
+Above command will start the server and then the mailman server will do polling in every 60 seconds(which is by default) to check for the incoming mail. However polling time can be changed by setting value to `Mailman.config.poll_interval`.
+
+`message_id` of email is also being stored in case we need to debug.
+
+***
+
 ## Bugs and support
 
 To report bugs and request features, please use the GitHub issue tracker provided at https://github.com/publiclab/plots2/issues