Dear notmuch developers, This is now the second time the following has happened to me: ######### $ notmuch show --decrypt id:xyz@example.com message{ id:xyz@example.com depth:0 match:1 excluded:0 filename:/home/simon/*** header{ John Doe <sender@example.com> (Today 21:52) (encrypted inbox new) Subject: foobar From: John Doe <sender@example.com> To: *** Date: Thu, 01 Jan 1970 00:00:00 +0000 header} body{ Failed to decrypt part: gpg: ASCII-Hülle: Version: GnuPG v2.0.17 (MingW32) gpg: <list of keys the message was encrypted with> gpg: AES256 encrypted data gpg: Original file name='' gpg: Signature from Thu 01 Jan 1970 00:00:00 UTC by DSA key ID <sender's key> gpg: Signature cannot be verified. Public key not found part{ ID: 1, Content-type: multipart/encrypted part{ ID: 2, Content-type: application/pgp-encrypted Non-text part: application/pgp-encrypted part} part{ ID: 3, Filename: encrypted.asc, Content-type: application/octet-stream Non-text part: application/octet-stream part} part} body} message} $ gpg --recv-keys <sender's key> $ notmuch show --decrypt id:xyz@example.com […] Hey there, Now the decryption worked! […] ############ Also, I should add that manually decrypting the message with gpg (i.e. without using notmuch) already worked *before* I added the sender's key (not shown above). Still, notmuch obviously doesn't like it when the sender is unknown. I hope you're going to look into this. Thank you!