This server is now running a Free SSL Certificate from LetsEncrypt.
I am running this server on Centos 6.7 and have plesk 12.5 installed. Now as a server Admin I prefer not to use control panels but I host some sites for a few friends and rather than having to manually add mailboxes etc I have Plesk running for their benefit. I also do a lot of support work for Plesk servers so it is handy to have a live Plesk server as a reference, development and for testing.
The problem with LetsEncrypt is that it requires Python 2.7 and Centos is limited to Python 2.6. The add on for Plesk doesn’t work for this reason.
The other issue is that I only have 1 IP address on this server so I need to support SNI to get SSL working across multiple domains.
I am currently doing a write up on how to get this all working together and should have it posted within the next week.
PS: I am running Centos 6.7 because I don’t like SystemD and specifically it’s binary logging first. If you want LetsEncrypt to just work on Plesk 12.5 I recommend using Centos 7.