Problems sending to local virtual domains

[Oscar Arranz]

Hi.

I have installed qmail with tcpserver and vpopmail.
When I send a message from a local address ([EMAIL PROTECTED]) to
an external account, it works fine
but when I send a message to other address in the same server it doesn't
work and puts a message like this on /var/log/syslog

        delivery 13: deferral:
Uh-oh:_.qmail_has_prog_delivery_but_has_x_bit_set._(#4.7.0)

What's the meaning of this?

Thanks in advance.