Distance study requires a lot of communication by e-mail. Try to form your messages so that they are relaxed but readable and friendly. Perhaps the following instructions might help you:

• Messages should be short.
• Write precisely, use punctuation marks and paragraphs otherwise the reader cannot follow your ideas.
• Write in a clear way. If you use colours be careful (e. g. yellow on white is very poorly visible).
• Put down the subject of the message. If the subject is not well written it can come among spam. The reader can delete it because he/she thinks that he accepted advertisment. Be careful to make a new subject if you start speaking about something else.

E-mails are not formal as letters but also not so informal as sms or oral messages. E-mails should not contain grammar or typing mistakes. It is very important that you answer to people who send you messages. Your answer can be very short, e. g.: Thank you, received. I agree. Welcome on forum, John.
If you do not like a message it is better to ask the sender how you should understand the message and then explain without anger that your opinion is different. In this way the person knows that you are trying to understand him/her and perhaps correct his/her statement.
Do not be personal in e-mails. E-mails in passive or impersonal form can sound rather dogmatic or too absolute.