Why did an index broke my config ?

[Denis BUCHER <dbucherml@hsolutions.ch>]

Hello everyone,

I added this in the config of my email server :
> index virtualdomain                     eq


But it broke the mail server, all emails were refused because Relaying
denied. In fact postfix was not able anymore to find domains.

For some reason, adding this index in the config made impossible to find
this domain for programs...

Don't know if my explanation is clear, but my question is "why adding an
index breaks the config" ?

Thanks a lot in advance for any help !

Denis