Adding external users to distribution lists

[Timotheus Pokorra]

> - Add 'contact' users with their mail address as 'External Email Address'.
>   'Primary Email Address' remains empty because of an error when trying to add
> the address there: "Email address '....' not in local domain."

Just for the record. We talked about that in IRC, and even filed a bug
report for that.
https://issues.kolab.org/show_bug.cgi?id=5127

Then I realized, that you can change the email validation of contacts
to basic, and it should work fine.
See details in the bug report.

Timotheus