The reseller from whom I bought the Google Apps Business account gave me a domain for testing the accounts BEFORE migrating.
It is working fine, I’m able to send emails to accounts using this domain (if I send emails to the real adress they will end up in the current server I’m using, not in the Google Apps accout).
But when I send an email to a group address using this test domain, no email gets delivered.
Best Answer
It seems groups cannot be created to respond to several domains at once - you have to choose which domain a group belongs to: http://googleappsupdates.blogspot.no/2011/07/create-groups-on-secondary-domains.html
The key phrase here is:
That would be the reason your group does not receive email sent to
group@testdomain.google.com.