A very long time ago, I published an Applescript I’ve created that uses Mail-Act-On 2 and MailTags by indev.ca to create a task in Omnifocus for messages you send out that you need answer or follow up (“Waiting For’s” in GTD terms). While I haven’t been working on the script ever since, the brave community in the Omnigroup’s Omnifocus forum did.
They refined the script, fixed some issues and when Scott Morrison from indev.ca got involved himself, the script evolved to utilise most of MailTags incredible power, e.g. using the project field of MailTags to add the task to the right project in Omnifocus if there is a matching one or even add a due date to the task based on the Tickler Date (if set) of MailTags.
Awesome community development. Make sure you check out the thread in the Omnifocus forum for more variations and further enhancements.
I believe the latest version has a bit of an issue and isn’t adding the task to Omnifocus, if the Tickler Date isn’t set. It still triggers the Growl notification, but the task never appears in Omnifocus. Hopefully I’ll have time to look into this and provide an update.
I’ve decided to leave the script source in the capable hands of the Omnifocus Forum community. Hence refer to the corresponding thread there to obtain the latest version and any updates.