Automation means using computers to make it much easier to send the same message to lots of people. It doesn't just mean a traditional mailing list or bulk mailing program. Writing any letter where you use a computer to insert the a significant part of the letter with text also sent to others is bulk mail. Having a computer prepare a raft of subtly different messages that mean the same thing is still automation. As noted, variants of a form letter are the same message.
Unrelated parties are people that have no personal knowledge of one another.
People who work together are related, but two people who both work for a large company may not be. People who have been debating one another in an online forum have a relationship but two people who posted to two different threads may not. The executives of a society have relationships with the members but unless it's a small society, two random members may not. The harm from 10-recipient mailings won't ve significant in the grand scheme. I would suggest a number like 25.