Review for SendTools by BamaPanda
Rated 3 out of 5 stars
It will work on the latest T-Bird. Look in the reviews for .."Change version this will run on'.
Even though it will not do a scheduled send repeatedly, I just made a template of the message that I wanted repeated and then set it up to send in 1 week intervals in the 'scheduled' folder. It helps to set each one up earlier than you intend to send it - time wise, so when you open T-Bird initially, it asks if you want to send the items in the 'unsent' folder.
Works pretty neat.
Maybe one day someone will improve it and make it totally automatic.
To create your own collections, you must have a Mozilla Add-ons account.