How to write an email in English

So, we would use the job title instead, which will not be offensive in any way.
Dear (name),
(eg.: Dear Mr Brown,)
In a more informal, semi-formal emails you could also greet the recipient by using his/her first name. It is quite common in offices when you correspond with somebody you know by name but they are not really close to you:
Dear Mark,
Dear Sue,
We often correspond not only with one person but with a whole group of recipients and then the most common salutations are probably these:
Dear Colleagues,
Greatings Colleagues,
Dear All,
The above forms are comparable with a small difference which may be important in some office situations. Namely, not all your recipients may be your colleagues and then Dear All is better. Remember also that colleagues in English doesn't mean friends. I found that for some students this word sounded a bit inappropriate in an office environment basically because of the fact that they associated it with Polish koledzy which sometimes really sounds more informal. Another thing worth remembering about colleagues is that it is, so to say, unisex. It applies equally to men as well as women. You do not have to worry about being or sounding a bit offensive then.
A salutation which is controversial these days is of course Dear Sirs, . I avoid teaching it at all, however, it turns out that many students ask about it. The problem is that it sounds and it is offensive and can be even sexist – just imagine what it sounds like when one of the recipients you address this way is a woman (!). It is definitly to be avoided these days.
If you have some more time to dig in this topic of salutations, especially the controversial ones, I recommend reading the following:
A discussion on Dear Sir/Madam - very eye-opening from a very...

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