With the increased use of the e-mail as a form of communication, I am questioning what is the correct form of title to those who would address in conversation as "Sir" My view, if you know the recipient, is to refer to him/her by name eg Major Bloggs". If you e-mail is addressed to more than one individual you should use the fomat "Gentlemen" or on occasions of informality "Gents" However I am increasingly seeing e-mails addressed to "Sirs" or even worse "Sir's". I believe this to be wrong. I have also seen e-mails addressed to "Sirs, Gentlemen", presumably to differentiate between those of senior rank to the writer and those of junior or equal rank. Presumably this would would lead to "Mesdames, Sirs, Ladies and Gentlemen" if addressing recipients of both sexes!