Although anonymous servers are abused by some people, they do offer an option for people who wish to speak candidly about personal issues, but keep their indentities private. A mailing list is a group of people who correspond via e-mail, usually on a specified topic. Mailing lists are usually like small newsgroups , and some mailing lists are mirrored in newsgroup form. Mailing lists tend to be free of charge. A bounced mail message is one which comes back to you with an error message, usually explaining why the message wasn't delivered.
Full mailboxes are generally only a problem with addresses at online services.
If you encounter this error you will have to try again after the individual or the online service has deleted some of their mail.