An Out of office Message is the autoresponder feature within your email settings that allows you to automatically send a response when an email is sent to a specific email address. Typically, businesses will use the autoresponder feature to confirm receipt of an email and to acknowledge and thank customers for an order that may have been placed.
I worked at an office where we used OOO messages on voicemail pretty regularly and if we forgot to change the message, our callers were quick to tell us the outgoing message was outdated. That end date feature would have been a big help for us! A local council in Wales needed to get a road sign translated into Welsh. (All official signs in Wales have to be in both English and Welsh.) They got an out of office message in Welsh from the translator they contacted, assumed that was the translation and printed the out of office message on the sign. They didn’t realise their mistake till a Welsh speaker pointed it out…

Note: Sending automatic replies to anyone outside my organization will send your automatic reply to every email, including newsletters, advertisements, and potentially, junk email. If you want to send automatic replies to those outside your organization, we recommend choosing My contacts only.
Note: You can also set different automatic out of office replies for different people. Just click the Rules… button in the bottom-left corner and add a rule for each person or email subject.