Writing emails in English isn’t all that tricky, but you have to know whether you’re sending a formal email, a semi-formal or an informal one, because the openings and closings may be different. This pdf document provides a short but nonetheless rather comprehensive overview of possible salutations and sign-offs: http://elt.oup.com/elt/students/result/pdf/br_pre_emails.pdf
If you’re writing an email to a woman, you have to know that Miss, Mrs and Ms are NOT the same thing and that you cannot use Mrs. for everyone. Read up on the differences between these forms of address and find out where they come from here: http://blog.oxforddictionaries.com/2011/11/what-are-mrs-and-ms-short-for/
This is important not just in writing, so you’ll have to know how to pronounce Ms as opposed to Miss. Most online dictionaries provide sound files; here is the entry for Ms in the Collins Online Dictionary: http://www.collinsdictionary.com/dictionary/english/ms?showCookiePolicy=true
Finally, if you want a short introduction to the psychology of cyberspace, check out this lengthy but humorous article on email communication and relationships. Section 3 on the anatomy of an email message, especially the bit on greetings, is particularly interesting: http://users.rider.edu/~suler/psycyber/emailrel.html
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