The encrypted mail has been supported for Android devices in Lotus Notes Traveler 184.108.40.206 (8.5.2 Fix Pack 2)
Lotus Notes Traveler 220.127.116.11 (8.5.2 Fix Pack 2) now supports encrypted mail on Android devices.
For digital signing, encrypting, or decrypting to work, the Notes ID file must be uploaded to the mail file or the ID vault.
It is necessary to click the "Download" button when you receive the encrypted mail.
You can see the option about encryption and sign when you tap the "Show Details" in new mails.
For more details, please see the wiki page, "Processing encrypted mail on an Android device" and have it now to point to this URL: http://www.lotus.com/ldd/dominowiki.nsf/dx/Processing_encrypted_mail_on_an_Android_device_LNT8521
The Lotus Traveler 18.104.22.168 Fix Pack release contains a number of fixes to enable this support.