I sent an email to someone who uses Outlook and Exchange, but I got an out-of-office reply because they are on vacation at the moment. Does that mean my message has been delivered, or was it simply bounced?
The out of office reply is something that a user can set and Exchange will automatically deliver to the sender when a email is received to their mailbox.
It is possible that the recipient can set a server based rule to automatically forward and/or delete any message that comes in, in which case, they will probably say in their responder - however this is up to them and is not normally the case.
If you exclude the above, in a typical setup, the response is just a response and when they get back, they should see your email.
You email was not bounced. The email was delivered. An out of office reply is a convience reply from the recipient to the sender (you). An out of office reply let's you know why someone may not be responding to your email for a bit.
As Wil noted, the recipient could create a rule to delete all their mail when they are away, but I have never heard of anyone doing this. I would expect any rules or filters they normally have in place would suffice while they were away.