Change the Administrators mail-from Adress?

[AlexSi]

Hi,

how can i change the mail-from adress which is used by plesk for system messages (i.e. apache alarm-level)?
Problem:

Domain mydomain.com is hosted by strato/plesk.
Mailserver for mydomain.com is mx.anotherserver.com
Administrator is [email protected]

Plesk sends the system message from [email protected] to [email protected], but mx.anotherserver.com needs smtp authentication if somebody wants to relay mail from *@mydomain.com to a *@mydomain.com adress.
Best option woud be to tell plesk to use [email protected] as senders adress.