Best to do this at the server via webmail access using a browser for the account.
There is an away or vacation message selection available for your .Mac account and AOL should provided the same.
Go to the .Mac website and select Mail to view received messages and your server stored mailboxes.
Select Preferences at the upper right above the message list and under the Other tab, select "Automatically reply to email when it is received".
Enter your chosen away message in the space provided and when finished, select Save at the bottom right to save the changes. When returning, repeat and deselect this option to turn it off.
This way you don't need to leave your computer on and the Mail application launched and running.
This thread has been closed by the system or the community team.
You may vote for any posts you find helpful, or search the Community for additional answers.
SET UP E-MAIL FOR 'IM AWAY'
Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.