Edit/Change "subject" on rules forward.
Many external to-do applications (Trello, Gneo for Evernote, Favro etc) have "secret" e-mail addresses I can post tasks to. However, they often rely on being able to edit/change the subject line of the e-mail. I would like to do this as actions within Airmail, however, there is no way I can reach the subject line via the rules settings.
For example, an e-mail comes in that I would like to act on, by creating a task in Gneo (which uses Evernote). That subject line would look something like this:
Original subject line of e-mail
I would then like to add to that subject line so it looks like this:
Original subject line of e-mail @Gneo Inbox #urgent #important
That would basically add which notebook I would like to send my evernote/gneo mail to (which is called "Gneo Inbox") and tag the e-mail with both "urgent" and "important" tags.
If this was possible I could then set up actions for regular "todo" (in Gneo), "urgent", "important" and "urgent & important".
Or, I could set up another set of rules for work, which uses Trello, where I could specify similar things (as noted here: http://help.trello.com/article/809-creating-cards-by-email)
I think there are lots of applications for this type of functionality.