[imp] Problem with user mail authorization ...

[Dos Wizard]

Okay ... updating to *Horde Groupware Webmail Edition* *1.1* wasn't so 
easy, I had to address various problems, but it's the only way I have to 
block outgoing spam by now. Anyway, some users, not everyone of course 
sees that annoying message after logging in.

User <someone>@<mydomain>.tld is not authorised for Mail.

Any ideas of how to correct it? The error appears to be random ... it 
doesn't happen on a specific domain, only some accounts act like this, 
others don't.
Even from the same browser, a mail account can login and use the Mail 
properly, some other can still login but it seems banned from using Mail.
Anyway to get some help over this?

Best regards
Nick.