More E-mail, Mailing List and Usenet Newsgroup Netiquette
Avoid "spamming",
the practice of sending unsolicited commercial e-mail messages in bulk,
or making similar postings to newsgroups. Spamming also refers to the
unkind act of purposely overloading someone's mailbox or server with
messages.
When sending or
posting to multiple mailing lists or newsgroups, indicate that you have
done so as follows:
"This message cross-posted to [names of mailing lists or newsgroups]"