sendTools

1. if you send regularly ( not send later or send at ) , the message will go directly to 'Unsent Messages' to be sent out on the 30 second interval.
2. if you send later, the message will go directly to the 'pending' folder and will only be sent out when you click 'file…send unsent messages' ( again, on the 30 second interval )
3. if you tick the send at box, the message will go directly to the 'pending' folder and sit there until the send at datetime is reached… if you tick send at and send later ( either with file…send later or with the send later button ( which shows up TB is set offline )) then sendat will override sendlater and the message will only be sent when the sendat datetime is reached.
4. if TB is 'offline' when any messages whose sendat datetime is reached, then those messages will queue in the 'Unsent Messages' folder until TB is set back 'online'

SendTools on Addons.mozilla.org