configs/voicemail.conf.sample - Make mailcmd sample text more explicit

Made the wording a bit more explicit. Didn't really change the meaning.
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Merged revisions 408876 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/11@408877 f38db490-d61c-443f-a65b-d21fe96a405b