Getting Things Done System: http://gettingthingsdone.com/
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ActiveInbox for gmail http://www.activeinboxhq.com/
Prior to switching to gmail I used Outlook, based on http://dynamicit.wordpress.com/2010/05/11/getting-things-done-with-outlook-2010-and-onenote-2010-a-brief-overview/
Several times during the email discussions I've thought that Active Inbox would do many of the things grey wants. Favorite features:
-Move emails to an "Action" category. -Schedule an email to show up at a specific date. -Make up your own categories. -Their system of using labels makes it work on any platform.
Downsides: -It's paid. Worth every penny for me. -Mobile app is still in beta.
I do the same thing Grey does in terms of moving up through emails and categorizing them and I find Active Inbox the first and only service with the right mix of clever features and minimal learning curve.
Depends on complexity of project, if it is just followups then a free tool like http://www.activeinboxhq.com/index.php should be sufficient, the only issue i see would be populating all the data the first time, then on maintaining it should be (!) easy.
Well here's what i do...I have 2 GMail account and 2 more google apps account for my business.
First off, I don't switch accounts...for the two GMail account I keep each open in a separate tab. I don't know which browser you're using, if Firefox I recommend you download the latest Minefield beta. It's pretty damn close to finished and it rocks. So with 2 GMail tabs it's barely pulling any weight, I wouldn't try it in FF 3.5.xx
I have all accounts forward an email when it arrives to my "main" account so I have a record of all incoming emails in one place which is searchable. Then I have a filter set up in Acct B which automatically BCCs any email that I send from that account to Acct A.
So far I haven't missed a beat, been using the system for about a month and I strongly recommend you try ActiveInbox (http://www.activeinboxhq.com/install.html... I'm not affiliated with them in any way) but it gives me a great way, one of the first that's actually worked for me to keep track of the various email todo's that I have between accounts.
Give it a shot...let me know if you have any questions :)