I have a little international business contact, and sometimes, some people write me a mail and address me as "Dear (my surname)", no "Mr", no nothing. Where is this common and how so? I never knew this. I only know "Dear (first name)" (American) and of course "Dear Mr (surname)", as well as "Dear (first name) (last name)". But this new variation, I can't quite grasp yet. Your input would be appreciated.
I see two possibilities: the first is that your correspondents come from one of the few social circles where Smith is a common form of address, and hence Dear Smith a common salutation. I haven't been in one such since my schooldays, but cultures vary.
Or it may be that the only information available to them is your surname, since somebody in the hierarchy is frightened of seeming sexist by providing gender. In such a case, Dear Mr, Miss, Mrs or Ms Smith would be even less friendly than the correct Dear Sir or Madam, so Dear Smith may seem a reasonable compromise.
Some countries will put their surname first then their first name (e.g. Smith, John) or they give an indication of heritage for example Smith; son of John; both of which would infer that the first name is Smith and not John. The person writing to you probably thinks that they are calling you by your first name and not your surname.
Alternatively if the correspondence has been automatically generated and populated from a database someone could have filled in the database incorrectly.
I have never used 'Dear Smith'in a letter, as I've never needed to (as far as I can tell). I have received such a letter, from the Deputy Secretary of the UK Government Department where I was working - I was 22 at the time. The D/Sec was the second to top man overall, so he was like God. He invited me to a drinks party, and I felt privileged to be addressed in that way as much as for the invitation itself. As far as I can tell, this form of address is semi-formal, i.e. formal because we hadn't yet met, while the occasion (or subject matter in the letter) was an informal one.