One of my colleagues (not a native English speaker) always ends his emails like this:
I guess he means Best regards with Bests. Could someone help explain?
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
It depends on where Mike is from. Perhaps there is a similar expression in his native language which he has tried to replicate in English. Or perhaps he has a personal reason for using this phrase.
However without that additional context, this is not technically a proper way to end an email. Here are some alternatives which are typical and similar (there are many more):