import re
p = re.compile(r'(?<=>)(?:mailto:)?([a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9.-]+)(?=<)')
test_str = "<b>dont:example@example.com</b>\n<b>mailto:match@example.com</b>\n<b>match@example.com</b>"
print [x.group(1) for x in re.finditer(p, test_str)]
aW1wb3J0IHJlCnAgPSByZS5jb21waWxlKHInKD88PT4pKD86bWFpbHRvOik/KFthLXpBLVowLTlfListXStAW2EtekEtWjAtOS1dK1wuW2EtekEtWjAtOS4tXSspKD89PCknKQp0ZXN0X3N0ciA9ICI8Yj5kb250OmV4YW1wbGVAZXhhbXBsZS5jb208L2I+XG48Yj5tYWlsdG86bWF0Y2hAZXhhbXBsZS5jb208L2I+XG48Yj5tYXRjaEBleGFtcGxlLmNvbTwvYj4iCnByaW50IFt4Lmdyb3VwKDEpIGZvciB4IGluIHJlLmZpbmRpdGVyKHAsIHRlc3Rfc3RyKV0=