[Osiris]

Faceted Browsing can be very helpful if you do not precisely know what you are looking for. It gives you choices which narrow down the search results. Seek is a Thunderbird extension that brings that concept to the email client. It displays mails by a variety of variables like recency, tags and from and offers a sophisticated search that narrows done the search results.
Searching can be done in two ways. In the first the user clicks on an entry in one of the variables, say mails since yesterday which blends all older mails out. The matching mails are then displayed in the mail folder as usual. The same principle works with every column, say tags or priority.
Search can be refined by typing in search terms. It would not be a problem to find all messages with the search term ghacks of the last two days, or mails of the last months that have been tagged with work and contain the keyword project.

Seek 1.0 extension to Mozilla Thunderbird from David Huynh on Vimeo.
One of the nicest aspects of this extension is the visualization which displays a timeline of incoming mails. The Seek [via Lifehacker]Thunderbird extension however has some shortcomings which I would like to address.
It does work best if you have all mails in one folder because it is folder based which is a pity because I tend to neatly organize my emails in folders and filter them on arrival so that they are moved to the correct folder. Makes it easier for me but this extension less useful.
The thing that’s bothering me the most however is the fact that you have to index folders before you can use Seek. That takes a few seconds only but you have to do it every time you change folders even if there has not been a change in that folder since then.
My default order of displaying emails is to group them by date which has been changed by the extension even if it is not active.
Last but not least you have to disengage Seek before you can delete mails in the active folder. The extension is great but it has those shortcomings which make it unusable for me unfortunately.
Providing a central index that gets updated whenever new mail arrives or is changed would be welcome because this is in my opinion the biggest problem of Seek currently.

Faceted Browsing for Thundebird