Culture, be it the company’s, industry’s, or a country’s, and unwritten rules of communication have an effect on how messages are received. Personal preferences are also good to keep in mind. Being polite and positive is a good rule of thumb for any means of communication.
When writing emails, consider keeping a formal tone and making an effort in the beginning at least. In time, a more relaxed approach might be ok, especially if the corresponding person initiates it. Cultural factors can be quite apparent with emails. For instance, in Finland people rarely use their titles and progress to a first-name basis quite fast. Then again in Germany, titles are very much used and addressing someone with their title is considered normal and appropriate.
Since email and other messaging functions do not include non-verbal communication, much of the subtle messages are missing. For instance, you cannot see what the person’s mood is, you can only guess based on the words or punctuation marks they use. And you can often also guess wrong. If you are not sure what a person is trying to tell you, ask them. Or if you do not want to ask them, trust the words. After all, no-one can expect you to be a mind reader.
Keep the above in mind when writing messages yourself. Be polite, positive and compassionate. Even if you are in a hurry, don’t leave out greetings, for instance. It’s often the details that make the most difference.