Review for Buttons! by sherkaner
Rated 5 out of 5 stars
I don't know what I would do without this extension. I use Thunderbird on a laptop, and in the course of a week, I'm connected to at least 4-5 different LANs, each with its own SMTP server. The "Select SMTP!" button is a real life saver.
To create your own collections, you must have a Mozilla Add-ons account.