Setting up Digital Certificate and Email Encryption?

[#1]

How do I setup a Digital Certificate and use Email Encryption in Thunderbird for my Plusnet email account?
Does it cost anything to do this or are there any free Digital Certificate services?
I am already signed up with a VPN service for the internet. How do I also encrypt my emails all the way from point A to Z?

[#2]

Firstly you'll need an installation of GPG (Gnu Privacy Guard) apropriate for your OS (not mentioned in your post so best not to assume). Then you'll need the Enigma mail plugin for thunderbird. You can then create your digital signature for an email address and have the public key automatically attached to outgoing mail. Of course the other end will have to set up something similar for an encrypted message between both parties.

[#3]

Quote from: john10001

How do I also encrypt my emails all the way from point A to Z?

And therein lays the "rub" - every receiving point needs to be able to decrypt the email... Or were you thinking about something else, such as SSL security to PlusNet's servers?  There is a thread about that elsewhere.