We have a need at my work to setup a test email server that will take all mail sent to it for delivery and instead just dump it into an account for later retrieval. I've been out of the email server configuration game long enough that I think that's possible but I don't know for sure.

As a more specific example of what we need: We have code that sends emails to outside clients in certain cases. We want to point our code to a test server that will accept those emails, but not let them get to the outside world (yes, it's happened before, oops). We then need to be able to verify that Email X would have gotten sent to Client Y if we had sent to the real server.

As a bonus, we have a error email alias on our real server that goes to the programmers that we would like to keep getting email from. So anything sent to that alias on the test server would forward to our real server for delivery.

My preference is for postfix but our IT staff seems set on using sendmail (or Exchange) for everything so hints/pointers for either server would be helpful. Thanks a lot.