Juan:'I have another question Peter, what should I write when closing an email in English?'
Peter:'Well, it depends on what you want to happen next. If for example, you've answered a question they had. I would write, I hope this answers your question. And then to be very polite you can offer them the possibility to contact you again about this, by writing, If you require any further assistance, please do not hesitate to contact me on my mobile. An informal way to say the same thing would be Give me a ring if you have any problems.'
Juan:'But what would I say if I was going to be on holiday or unavailable? In a formal way.'
Peter:'Then I would start with I will be out of the office on Tuesday. Then after that, If you require any further assistance, please do not hesitate to contact my colleague Sally Smith on etc...'
Juan:'What would I say after that sentence and before yours sincerely?'
Peter:'If you expect to have more contact with the person, I would write I look forward to hearing from you. You would use that if you expect the contact will be by phone or email. If you are planning to meet or visit them in person, then 'I look forward to seeing you' is what you write. A more informal way to say the same is to change the tense of the verb 'look' in the sentence to the present continuous. For example, I'm looking forward to hearing from you.'
Juan:'If I want them to do something quickly. How could I write that in the closing part of an email in English?'
Peter:'If you want to be very direct and aggressive, you could use Please deal with this matter urgently. Or you can be politer by writing, I would really appreciate it if you could deal with this matter urgently.'
Juan:'And lastly, how could I write 'I'm going to contact them on Tuesday'?'
Peter:'Easy, I will contact you on Tuesday.'