Emails have long become the de-facto form of communication. Thanks to this, a volume of email  is sent and received. This makes it imperative for communication over emails to be clear, precise, and unequivocal (meaning, there is only one way of understanding something)

Here are some tips that will help you send better letters/emails:

1. Send brief, clear messages.

The shorter the email, the greater the chance it will be read. Using short clear sentences is always a better way of presenting information. In other words, do not use big words and over long sentences.

2. Send multiple messages for more than a few topics.

If you have many topics to address, send each one as a separate mail. If you have to send all that in one mail/letter, use paragraphing. This will ensure the mail is clear and has more chances of being read.

3. Include relevant information from the past.

The reader might not have such a great memory as you do. They might not remember where the last conversation has left off. Make it easy for the reader by giving some lead into what the last interaction was about.

4. Write clear descriptions.

The reader should know exactly what you intend in the shortest possible way. 

Ex: In today's competitive era, computers are vital in helping us in doing many things. One of the most important of which is learning.
Better: Computers have become an important tool for learning.

5. Jargon and Abbreviations

What might be something common for you, might not be so for others. When you say, I am having problems with docking in the port. You could be talking about computers or ships. And if you are writing about to a shipping company about computers, or about a shipping company to a computer guy - things can get messy real fast.

The same goes for  abbreviations: DET could mean the Duolingo English Test or the Diploma Entrance Test!

6. Proofread. Proofraed. Proofread.

If you have noticed, there is a mistake in the second word of the sentence. You will notice errors that you might have missed the first time around. So, save some time to proof read before you let the mail go away from you.