dstiles - 10:49 pm on Mar 28, 2011 (gmt 0)
I use Thunderbird, although not as an IMAP client. I once tried IMAP under Windows but only as an experiment as I prefer mail to be under my full control - ie on my computers not "theirs".
I use email intensively (several hundred accounts at one time), including "forging" From, Reply and Sender addresses on occasion. There are several niceties for Thunderbird but some require add-ons: address switching is one of these.
My own add-ons include:
Display Mail User Agent
Quicknote (set to 4 panes)
Quicktext (very useful boiler-plate text insertion)
Signature switch (change sigs on the fly)
Virtual Identity (change email addresses on the fly)
Xnote (tag listed emails with pop-up info)
Some of the above may not be suitable for IMAP.