The documentation is current and valid. I rewrote the relevant parts of it as we were developing version 4.
1. This is an optional feature. To enable this feature you need to 1. Set up the mail server information in the Akeeba Ticket System – Mail Fetch plugin; 2. Enable this plugin; 3. Set up the email addresses in each category; and 4. Set up a CRON job to trigger mail retrieval. None of this is done automatically for you. Therefore, if you have not manually done all of the above the Reply by email feature is not enabled. Likewise, if you HAVE done all of the above you also understand that disabling this feature is as simple as removing the CRON job or unpublishing the plugin.
2. The plugin only provides the CRON command. You still need to run a CRON job to trigger it. You can use either the CLI script or the web endpoint for your CRON job. There's a page in ATS showing you how to do that and there's of course the documentation https://www.akeeba.com/documentation/akeeba-ticket-system/cron.html
Nicholas K. Dionysopoulos
Lead Developer and Director
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