O365 

One Support Mailbox

Two support groups, emails are aliased to the above mailbox.

Business Rule: If sent to A place in group A, if sent to B place in group B

When an external email comes in to either alias it gets placed in it's respective group correctly however when a user on the same domain emails it is ignored and the rule is not applied.  This is possibly because Exchange just uses the default mail address or x500 address so ignores the aliased email address.  It was like this on our previous set up of EX2007 so we created two seperate accounts and have them forward the emails to the main mailbox.  Now we pay for each license (mailbox) we would like it to work as it is supposed to.

Any help?