Heya, please find attached the second take on adding support for messages that lack Message-ID to notmuch-mutt. For context see http://notmuchmail.org/pipermail/notmuch/2015/thread.html#20079 In this new verison of the patch we start computing the SHA1 incrementally, in case no Message-ID will be found. As soon as the header is over we parse it (using Mail::Header, to properly handle line breaks). If a Message-ID is found, it is retourned and SHA1 computation on the rest of the message is aborted. If no Message-ID is found, SHA1 computation continues, and is used in the end to synthesize a fake Message-ID in the same way that notmuch itself would to. Note that, contrary to the previous version, no changes of the Debian packaging are needed this time: Mail::Header is contained in the same package of Mail::Internet that notmuch-mutt was already using, and Digest::SHA is shipped with Perl itself. Please consider applying this patch to notmuch's master branch. Cheers.