Rated 5 out of 5 stars
Thank you to the developer because this add-on is mandatory for my life. I routinely write messages at 2AM to be sent out during "normal business hours" later that day. I would need to stop using T-Bird if this extension were not available. Frankly I don't know what I would do because no other email client does what I need (Gmail isn't an option).
I haven't had any issues regarding "spamming" or multiple sends. I will update this review if I do. I only have SendLater check the drafts box every 10 or so minutes, however -- not every minute. I don't need to specify the exact time that emails need to be sent. Perhaps changing that default value might help?
I ran T-bird 2.0 for years, then two years ago switched to 3.1, and only a week ago switched to the latest version. I am wary of "upgrades" because my email system needs to be absolutely bomb-proof or I stand to lose a great deal of money. I used the Mail Tweaks "Defer" add-on for years which worked fine, but this seems to have more options and I'm looking forward to integrating it into my business and my life.