Exchange 2010 (SBS 2011) multiple domains for email users

Hi Guys,

Have been doing some digging and I haven't been able to figure out how to do this.

We need to host multiple domains on our exchange server in such a way that users will be able to send and receive emails though their single outlook mailbox.

For example

username@mydomain.com can send and receive emails as username@mydomain.comusername@2nddomain.com and username@3rddomain.com (there are 5 domains in total)

Also we don't have a clear cut list of which users need to be able to do this. maybe some from sales, marketing and even support. its probably going to evolve over time.

I followed this thinking it would solve the issue

http://community.spiceworks.com/topic/148907-can-exchange-2010-send-email-s-from-multiple-domains-ho...

But I get this response if I try to send an email as another domain

Deliveryhas failed to these recipients or...