What better Solutions? Outlook? Windows Mail? Mac Mail? Web clients (any of them?)... pff....
I'll give the folks who like Evolution on Linux a tip of the hat.. .but Thunderbird is *way* better any any of those others mentioned.
Full End to End Encryption solution out of the box.
Easy to move profiles whole and intact between computers, even between operating systems.
Can handle 100 of GB of e-mail without issue.
Functional and easy to train spam filtering.
All told, It's a great product,, and I would say, more important now than ever before. (For the Encryption feature.)