authentication with '@' included in username

[Patrick]

Hi all,
I'm using

        FreeBSD-4.3-Stable
        sqwebmail-1.2.4 (built from the ports)
        Apache/1.3.12 (Unix)
        Sendmail 8.11.3/8.9.3

I tried adding a few hosts in logindomainlist and now all authentication
fails with a "Invalid user or password" error.
Removing logindomainlist promply gets rid of the error.
However, I need logindomainlist to support multiple virtualhosts on the
machine

My question is why are users only authenticated without the '@domain' and
if I have to do some mapping and if so how.

Thanks.
Patrick