With Forwards you can choose to send a copy of all your incoming messages to another account while also optionally maintaining local delivery of the messages.

The Away Message lets you set an Out of Office reply

User Extensions allows you to uniquely extend your e-mail address in order to create disposable addresses. Extensions take the form user-extension@domain.com and can either be defined by the user or left as wild cards. 

They can also be very useful when dealing with shared mailboxes but when you still need to address someone in particular. A support team will have the address support@domain.com but an individual user from the team can give out support-joe@domain.com as his address.