I’ve got a little technique I want to share, that I’ve found very effective lately.
The role of Project labels isn’t always obvious, especially in email. For more casual users, especially if they use multiple task managers, it doesn’t make sense to track their “main projects” in Gmail (the emphasis is on the things they understand as “projects”, in the sense of “this is a work project”).
But the great weakness in email is not ‘email overload’ – I don’t believe it exists in a pure sense – but the fact that email is an open “catch all”. It is so simple, and used by absolutely everybody, that it becomes the obvious choice for communicating about ABSOLUTELY EVERYTHING. So there’s not an overload of email, there is simply no focus in email.
In a very real sense, projects partition emails into manageable “streams”. In full GTD, a project is not a “thing” in itself – it’s not well defined – it’s a group of related tasks that are not yet finished. You might think you have a project to “refurnish the kitchen”, but actually its a set of related tasks that keep going until you run out of tasks. The project doesn’t end, the tasks do.
So far this might be very obvious to you! But I think it’s a very powerful idea. And for those of you who are saying “yeah yeah, get on with it”, I hope I have an interesting next level for you 
There are many different types of conversation, and some conversations are so identifiable that they can be defined by the common path they take. A pipeline, if you will.
For example, in customer service, you 1) receive a request, 2) reassure that person you have heard them, 3) find out more details about the problem to try and find a solution, 4) tell that person the solution.
And for public relations, for a specific announcement, you might 1) Tell a member of the press the announcement, 2) get a reply asking more information or at least acknowledging it, 3) get confirmation they’ve written about it.
The pattern is so precise that you can codify it to repeat it. For example, I use the label format:
P/PR/<Campaign>/1) Contacted
P/PR/<Campaign>/2) Responded
P/PR/<Campaign>/3) Written
I then move each individual conversation through these pipelines.
There’s all manner of reasons why you’d do this – to educate a team about company processes, to ensure every contact is satisfied by your response (in the customer service example), to keep things moving forward to your goal (in the case of PR). And ultimately, for an overall sense of control & flow.
Implementing this is trivial with ActiveInbox; just use the number/bracket prefix on a label to order it.
There are two broad approaches depending on how well defined something is.
1) With something like the PR campaigns, it is a campaign, so you can create the necessary labels and reuse them a lot. The same example again being P/PR/<Campaign>/<Step>. More generically, this is P/<Type>/<Name>/<Step>. (The emails are mostly outbound).
2) With customer service the problems cannot be predicted. So, you give a project label for the problem (P/Issues/<Bug Name>, in our case); and have a category for the pipelined process (Pi/TicketFlow/1) Received -> Pi/TicketFlow/2) Acknowledged, etc.). (The emails are mostly inbound)
Oh, and while in future we may find a better way to have ActiveInbox support you doing this, right now I find ‘pin’ing popular labels a huge help.
As ever, it will be great to have your own thoughts on how you use projects in email; and any similar experiences you have. Please comment below!