Yeah, you are right. Unwanted messages and emails are the only worst thing in LinkedIn. Sometimes, I got 30-40 emails from LinkedIn which are useless for me. I don't know why people pay LinkedIn for marketing? There are many other ways through which you can do marketing of your product or business in free. The best way is to write different articles about your products on different groups of LinkedIn. Millions of people are using LinkedIn, So your post on different groups will really help you, but before posting I will suggest you learn the difference between LinkedIn article LinkedIn post.