Creating group for external users

I would like a group which include users found in our domain and other external users… Could someone help… I have try to create a group but when I try to do Reply All it looks for a domain… What are the steps to create a group including external users… Thanks

Subject: Creating group for external users

You can just enter internet email addresses into groups, which should be OK for you

Subject: RE: Creating group for external users

That’s what I hv done…but the problem is as follows, I create a group say ‘Group Test’ from the public address book with addresses which are as follows: xxx@mydomain.com

yyy@domainyyy.com

zzz@domainzzz.com.

When I send a mail to Group Test from mydomain.com and from domainyyy.com I try to reply to all, by default it takes the address 'Group Test@mydomain.com.

Most grateful if someone can help… Please.