Acceptance of academic email endings I am looking for statistics for the acceptance of email endings in the academic community. I was informed that "Best regards" and "regards" are among the best ones. Is this true?

For example, this is a good source for the appropriateness of email salutation:
https://thermaltoy.wordpress.com/2013/01/26/dr-who-or-professor-who-on-academic-email-etiquette/

From this source, about half of US professors prefer "Dr.", while the other half prefer "Prof.". How about "Prof. Dr." so we won't miss anything?

I also notice that a lot of members here recommend the email-writers to mention the connection between the writer and the professor. Is this always very important? Is it cost-efficient to go to conferences to meet with potential PhD advisors (I meant time-cost. $ is out of considerations.)? 



Some related good stuffs
How much detail to include in first email to potential PhD supervisor?
I don't have statistical data on this (and I doubt any exist). Personally I find "Best regards" and "regards" to be very formal, but it depends on who you're speaking to.

I prefer to use "Best wishes", "All the best", "Best" (if the email is brief or we're in a hurry) or "Ciao" (my supervisor is Italian).

As for salutations, I don't think Prof. Dr. is used anywhere outside of Germany, because usually only the most recent or senior title is used. In other words, use Dr if they're a PhD and Professor if they're a professor. If you don't know which they are, find out.