I often send and receive gpg-encrypted mail. At the moment I use thunderbird + enigmail (in linux) to do that. As far as I know there is no way in thunderbird to find all encrypted messages which bodies contain particular keywords. There also seems to be no option to save encrypted mails decrypted (so they would be searchable). However for me it is important to be able to search old encrypted mails. So my question is:

Is there a way in linux to save incoming mails automatically decrypted in my inbox and save outgoing encrypted mail decrypted in the send folder? Both times adding a line to the body which remarks that the mail was encrypted.

It could be another email client for linux that could to that or perhaps a solution using procmail or maildrop.

For a procmail solution I guess there could be some problems with encoding (perhaps one have to use emil?). Note that the solution should work for multipart encrypted messages (including encrypted attachments) too.

Further note that I don't want a discussion about security holes. For me it's ok if messages are stored decrypted on my harddrive (which is encrypted as a whole anyway). In doubt for a first solution it would be ok to store my private key passphrase in cleartext on my harddrive, too. The point is that the mails are encrypted on the mailserver or more generally on their "way through the net".