I have both Kunena and Jomsocial on my site. For both, our users receive notifications by email. I'd like:

1) A step-by-step guide on how to set up Post By Email for our users to reply to forum topic notifications by email.
2) A step-by-step guide on how to set up Post By Email for our users to reply to Jomsocial notifications by email.

Hello. Here is Post by Email documentation.

This screen will help you also:




Kunena: you must setup email box in post by email. Email box must be the same as "from" email of Kunena. Than just setup this box - you have full control in Post by Email - you can select post as new topic or post as reply and reply tags.



JomSocial:
You may choose where to publish the emails content in JomSocial: on the wall or as status update. If you choose to publish it as status update, you can control whether the "Comment" and "Like" buttons are enabled or not. (only version for Joomla 2.5 support JomSocial)