Your post appears to ask for a commitment. Before you asked the questions.
Try this. Post in say the CNET Computer Help forum but go ahead and drop a few questions. If you ask 20 questions that doesn't work well. Try one or two.
Want to replace Thunderbird. Went from OE reconfigured to windstream.net and then TB. Mailbird sounds good but have questions about use that Mailbird HELP is no help. I am networked, 5 computers, using XP, 8.1, or 10.
Anyone interested in helping?