what does this mean?

[em`s]

Jan 23 19:03:30 server qmail: 980247810.020311 status: local 1/10 remote
0/20
Jan 23 19:03:30 server qmail: 980247810.032344 delivery 29: deferral:
Unable_to_find_alias_user!/
Jan 23 19:03:30 server qmail: 980247810.032445 status: local 0/10 remote
0/20

what does Unable_to_find_alias_user!/ means??
what can i do to fix this??

thanks//







 e m ` s ([EMAIL PROTECTED])
  U r l : http://ems.ath.cx