[imp] vacation problem --Data format error

[alex]

Hi there:
I enable vacation for my account successfully,but others mail to me got such 
returned error message

   ----- The following addresses had permanent fatal errors -----
"|/usr/bin/vacation alex"
    (reason: data format error)
    (expanded from: alex@thbuo.gov.tw)

----- Transcript of session follows -----
501 5.6.0 Data format error
procmail: Lock failure on "/var/spool/mail/c600575.lock"

My mailserver is sendmail 8.11.X and I sure that vacation was found 
at /usr/bin/vacation and here are the files for my vacation setting:

[.forward]
\alex, "|/usr/bin/vacation alex"

[.vacation.msg]
Subject: On vacation message
I'm on vacation and will not be reading my mail for a while.Your mail will be de
alt with when I return.

[.vacation.db]
BLANK

[.vacation.dir]
BLANK

[.vacation.pag]
BLANK