I know that it might be annoying. Still the answer to your question is: No. You cannot just add a huge company to a block list based on your own opinions. Someone actually wants to get email from LinkedIn. Nor is there any list that is The Spam Blacklist that would solve the problem.
You need to make the configuration locally on your server. Since you haven't provided any information about your server configuration and even the software used, we cannot help you with specific instructions.
Anyway, I discourage making any server wide blocking if you aren't absolutely sure that none of your users is willing to receive email from LinkedIn. Best way to handle this is to use personal filters:
- On Unix/Linux systems you can add filters using e.g. Procmail or Spamassassin.
- On Exchange Server environments you can add filters in Outlook or OWA.
Which actually makes this more relevant on Super User than Server fault...