how to have a mail account name different from shell account name

Henry Nelson <[email protected]>
Newsgroups gmane.os.netbsd.help
Message-ID <[email protected]> 
Forever I've just let the mailbox name for Sendmail automagically be the
same as the uid.  Is there some "simple" way to change the portion before
"@" of an e-mail address so that it is different from the uid, and that
Sendmail will refuse to receive e-mail addressed to the uid (return "No
such user"), and only accept mail for that user addressed to the specified
"e-mail name."  TIA

-- 
henry nelson
  WWW_HOME=http://yuba(dot)ne(dot)jp/(tilde)home/
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