There’s our Hook productivity app for Mac that addresses this issue on Mac, but more generally. I.e., not just with mail but with anything. Basically, Hook enables you to link almost anything to almost anything. So you can
- select an email message,
- invoke Hook, and
- Select “Link to New” (⌘N),
and a note in the default note-taking app will be created. Works with Apple Mail, MailMate, Outlook and AirMail. Part of the beauty is that your notes are not stuck in the email client. If you switch email app, the links between messages and notes will still work. Readdle’s Spark email client lacks AppleScript support unfortunately so they don’t support this yet (perhaps user demand will have an impact there).
Here are examples with Mailmate..
Hook is very lean. It just provides the links between individual items (e.g., mail, PDF, web pages, documents, files, etc.). Whether the “note” is an diagram (e.g., OmniGraffle), task (e.g., OmniFocus, Things, Task Paker), other document (Pages, TextEdit, Word, Brett Terpstra’s nvALT or nvUltra etc.), etc., is mostly up to you. Hook can even auto-store linked notes in personal information managers like Evernote and EagleFiler. (Hook’s support for Tinderbox is coming very soon based on Rob Trew’s scripts. (Hook is highly scriptable.))
However : Hook’s not on iOS yet. But you can setup Hook to store your notes in the cloud so you can get them on your notes. (E.g., in Dropbox, Documents). Or Hook can auto-create Evernote notes. Naming conventions can also be used in Hook so that you can quickly access your notes on iOS with Spotlight.