Howto change email address of a user to "unknown" with repotools-jts?

Dear all,

we manage the user DB with help of external script which feeds repotool-jts. This we need because we have multiple LDAP base in our company and use federated repo in WAS.

Now we have the problem, to change email address of users in the DB to "unknown".

We tried following command:

%JTSrepotoolPath%\repotools-jts.bat -createUser userId=imp_buildaccount@dom1.company.net name=imp_buildaccount emailAddress=unknown repositoryURL=%JTSHostURL%

Unfortunately the email address is not set to "unknown" like written in the help of repotool.
On the other hand the same command with a valid email address is set the email address in the user DB correctly. So the command is correct, but the keyword "unknown" seems to be wrong.

Any clue?

regards
Guido