1. Should. You should do this so that people can know what the email is about before hand.
2. Shouldn’t. You would be forwarding the email to people who had already received it.
3. Shouldn’t. You could be advertising your email address to people you don’t know.
4. Shouldn’t. You should use the “bcc” field in this case.
5. Shouldn’t. Your email address could be hidden for a reason.
6. Should. People may not know who you are by your email address alone, so it is necessary to include both.
7. Shouldn’t. This will give other people’s addresses to people they might not know.
8. Shouldn’t. This is a chain mail and you should just delete it.
9. Shouldn’t. Not everyone has time to look at cute pictures of puppies and you would just be taking up space in their inbox.
10. Should. You wouldn’t want your email address all over the Internet, so you should respect the privacy of others.