From: California, USA
Just to confirm your understanding of OOF (the abbreviation used by Microsoft), a message is only returned the first time a unique sending address sends a message to a mailbox, not a particular recipient address.
As an example, let's say I have a mailbox where my primary SMTP address is email@example.com and I also have an alias on the same mailbox firstname.lastname@example.org and I've enabled OOF.
If you sent a message to my abc.org alias as the first message to me, you would receive the OOF message in return. If you then sent a message to my company.com address, you would not get an OOF. Likewise, if the first message you sent was to company.com you'd get the OOF and if the second message was to abc.org you would not.
Dean T. Uemura
Microsoft MVP - Exchange (2007-2011)