As far as I know the only one that works on 8.0.7:

Zimbra OpenPGP Zimlet alpha development version 0.2

To install follow the read-me:

https://raw.githubusercontent.com/ba...ster/README.md

Bug reports here:

https://github.com/barrydegraaff/pgp-zimlet/issues

How does it work, video:
https://vimeo.com/93372197

Alternate download link for the video: https://drive.google.com/file/d/0B_l...it?usp=sharing