[horde] imp signature doesn't work

[A. Schulze]

Jens Wahnes:

> The only exception are hooks.
> Those are to be put directly into hooks.php, not hooks.local.php
> (examples for hooks can be found in hooks.php.dist).

why?
my hooks work fine when placed in hooks.local.php or hooks.d/ or  
hooks-FQDN.php

Andreas