Domains with external Mailserver

[memic]

Hi,

ich have serveral Customers which have an own Mailserver and if i send mails
from my server to them, i get problems cause they have a postfix config (which is
not used) and the mailserver trys to deliver to himslef and doesnt find any emailaddresses.

is there a solution for this? would be nice to have no postifx config at all if there are no email adresses created..

thx in advance..

memic