Hi Yuhua J.,
K9 Open Source mail Customisation:
Change All logos
Add Password screen with wipe after 5 incorrect attempts
After the passwordscreen you will see these maps:
INBOX ( we will call this Encrypted Messages)
After pressing on Encrypted Messages:
You only see messages you received and sent. All messages will not show preview lines or subject. ( All subject must be secret until message is opened)
The header will contain the title of the map and under the title you’ll see your email address.
On the footer you will see Search Icon, Lock Icon (will lock the app), Filter Icon, Sort Icon, Write email Icon and Settings Icon.
Settigs Icon will offer you this: Select All, Mark All as Read, Check Mail, Add Contact, Go to oldest Mail, Go to newest mail.
When you go back to the first screen, you will see Saved Messages, these messages are saved from the inbox.
When you go back to first screen, you will see CryptoVault. Vault will let you make pictures in to the storage, Create notes and let you attach in to
mails. Also all attatchments will be stored in there.
If you go back to first screen, you will see settings. The most settings will be removed. You can leave these: Theme, Language, CryptoGraphy ( Needs to changed to Encrypted Keys), Add Security Time out( minutes that will lock the screen), Change password ( to change password for lockscreen), Clear Public Key Cache (will clear cache of all stored pgp keys) , Wipe, Will empty mailbox and contacts, Message Self-Destruct Default Time ( time for the burn message), and Default message expiry and deletion (the time a message will be removed from the inbox automatically)
If you go to Cryptography you can remove the second question and the first question will be change to PGPKeyCreator instead of OpenPGP App. (the openpgp app is also opensource and will need customisation soon)