If you have hundreds of thousands of emails within reach of thunderbird it will by default download all of them. Try to index all of them. And it will devour your CPU and disk space and RAM to do it. Every time I set it up again for the first time it's a race to turn off the excessive indexing before it irreversably decides to chew up gigs of my disk and permanently be stuck using at least 2-3GB of RAM when loaded. And it's really hard to find all the indexing options.
For a company that built its reputation on search, google's ranking of results are remarkably crap. I often find myself spending multiple minutes trying to find an email I know I replied to just hours before and they just never show up. Terrible...
For instance I can't specify that I am looking for mail either to or from a specific sender trough the search UI, only mails with an address as both to/from, which litters the results with mailing lists that have 100s of recipients.
Due to this, I often resort to zimbra for searching my mail box. The interface is much more effective.
It doesn't help that, at least the French version, the menu entry for that function is cut (and looks like "search in m..."). "Advanced search" (the window title) sounds like a more descriptive and better title.
It'll be a separate address book from Thunderbird's
