Buzzwords, slang, clichés, and jargon have meanings that are culture dependent; they can only be understood within a cultural setting in which the society has agreed upon a non-literal meaning. This means that each of these types of expression are figurative, non-literal, figures of speech. For an example of this, if Americans say, "Money flies out the window," it is agreed that this idiomatic figurative expression means money is quickly gone or even wasted. Business correspondence is directed to people from many backgrounds and national origins, especially in this era when so much business is international. Therefore correspondence is most successful when free of culture dependent figurative expressions.
If business correspondence contains buzzwords, slang, clichés, and jargon, which is technical language that is used in a particular trade (e.g., "endcaps" of retail), the risk is run that the communication--which can be supposed to be important--will be imperfectly understood or even completely misunderstood. If the point of business correspondence is to successfully communicate, and it is, then business correspondence must employ straightforward literal language.
This is an important question. When a person is corresponding with another person, especially in a formal setting, such as business, then it not good to use slang, cliches, and other non-professional jargon for at least three reasons.
First, people make assumptions based on our use of language. So, if we use language that is not correct (such as slang), then people may conclude that we are not educated. In light of this, you might lose the deal.
Second, in a more formal setting, where you are dealing with people from different backgrounds and ages, there is a good chance that not all people will understand slang or buzzwords. In light of this, it is best to speak in a more formal way.
Finally, there is a professionalism that should be maintained. If we do not, then we might not be seen as respectful. There can be offense and the upshot might be the loss of business.