Dear Dr. vs Hi vs none in E-mail communication [closed]

Unless the recipient of the email is a superior or the context of the email calls for formality, I would expect this to suffice:

Dr. Lastname,

Body of email.

Firstname

Efficiency and directness usually supersede formality in email. Even my correspondence with superiors (Professors, Managers, etc.) tend to devolve into the format above after my initial message, and sometimes lose all salutations, leaving a text message like format.

When in doubt, I look to the format they choose for their reply and respond in kind.

Hope this helps.

As Baz says, this is more culture and etiquette than English, but ...

I never write greetings or signature lines in an email. It seems to me that the "To" in the header is the equivalent of "Dear [whatever]" and the "From" is the equivalent of "Regards" etc.

I think this is comparable to a printed office memo with "to" and "from" blocks at the top. You do not write a "Dear Al" and a "Sincerely, Bob" on an office memo, because these names are already in the "to" and "from" blocks. http://www.ehow.com/how_5025751_write-interoffice-memo.html