<i>Any typo that aborts program execution will cost you mail. Any bug that manifests someday in the future will cost you mail. [...] For over a decade, I was so fixated on doing the mail processing during delivery that I was blind to the much simpler approach that was staring me right in the face.</i><p>So, why not even go a step further and treat maildir as append-only storage? Do the deletions, mark-as-read, and attachment inspection using notmuch. This is one of the really cool things about notmuch: it gives you a mutable view of &#x27;immutable&#x27; mail storage.