Based on Speed, Privacy and Security Mailpile provides:
- OpenPGP signatures and encryption as part of its core design, not an afterthought or plugin.
- A fast and responsive mail client, outperforming "the cloud" even on slow computers.
- Storage of your mail on devices you control, your search index is encrypted so if your computer gets stolen, your mail stays secure.
Read more and download mailpile from here - https://www.mailpile.is