no need to build - learn to use pgp
there is no need for anyone to build anything. for secure mail what you want is already available,-- for free.
start by switching to Linux,-- I recommend MINT
read and follow instructions regarding maintenance: stick to the official software store.
switch your e/mail to a commercial supplier -- not one of the free ones like Hotmail, Google, or Yahoo. I use Charter, and CoreComm services.
next switch your e/mail onto the THUNDERBIRD client -- that comes with Linux/MINT (also Ubuntu if you prefer ). spend a little time learning to use Thunderbird. it uses IMAP servers -- so you can share mail on your iphone (that isn't encrypted) .
activate the ENIGMAIL plugin on Thunderbird. this uses the GnuPG version of PGP.
use the OpenPGP dialog on Thunderbird to generate your PGP keypair. set 1 year expiration date; load your public key to the keyserver. be sure to generate and save the key revoke certificate (JIC).
locate, dowload, and read Phil Zimmerman's essay on PGP, paying particular attention to the section on protecting public keys from tampering. learn what the Trust Model is -- and how to control it.
find a pardner to begin exchanging PGP mail with
remember there are 3 main advantages to PGP (ENIGMAIL) mail
authentication allows you to ascertain with reasonable certainty that an e/mail is from the party which clains to have sent it. without this i can send you an e/mail and mark it from anyone i want -- your boss -- or Nixon or Kruschev
integrity allows you to be reasonably sure that you have a correct copy of a message; that the message has not been modified in-transit by someone using (e.g.) a "Man in the Middle" attack. This is CRITICAL for software distributions and financial transactions .
security allows you to encrypt messages so that you can be reasonbly sure only the intended recipient can read them . this is a lot better than putting a disclaimer in your signature block saying something to the effect "if you weren't supposed to get this please cover for me, thanks"
NSA can still apply a traffic analysis on you: ascertain who you are talking to and this won't ever go away on public networks -- switched circuit -- or packet switched . but to get the messages now they have to hit YOU with a subpoena. hitting your ISP won't help: Your ISPcouldn't read your traffic in any reasonable timeframe or at any reasonable cost -- no matter how much they wanted to .
remember though you are subject to the AUP you signed with you ISP. the government could tell ISPs that PGP mail traffic must not be allowed. in which case we'll come up with a new Plan .