import re
pattern = "(?:\\b[Tt]o:|\b002;)\s*(.+?)\s*<[^<>@]+@[^<>@]+>"
mystring = 'To: John Lennon <John.Lennon@gmail.com> \b002; Paul McCartney <Paul.McCartney@yahoo.com> \b002;'
print(re.findall(pattern, mystring))
aW1wb3J0IHJlCgpwYXR0ZXJuID0gIig/OlxcYltUdF1vOnxcYjAwMjspXHMqKC4rPylccyo8W148PkBdK0BbXjw+QF0rPiIKbXlzdHJpbmcgPSAnVG86IEpvaG4gTGVubm9uIDxKb2huLkxlbm5vbkBnbWFpbC5jb20+IFxiMDAyOyBQYXVsIE1jQ2FydG5leSA8UGF1bC5NY0NhcnRuZXlAeWFob28uY29tPiBcYjAwMjsnCnByaW50KHJlLmZpbmRhbGwocGF0dGVybiwgbXlzdHJpbmcpKQ==