The Out-of-Office Assistant is missing
Out-of-office Assistant is for Microsoft Exchange mailboxes only. Look for it on the File menu is Outlook 2010 or on the Tools menu in older versions.
If you don't have an Exchange mailbox, you'll need to replicate it's actions using Rules Wizard, or better yet, use your email server's "vacation reply" feature to send out-of-office replies. When you use Rules Wizard to send Out-of-office replies, Outlook needs to be running and checking mail regularly for the reply to be sent. Using your server's "vacation reply" feature allows the response to be sent when the message arrives, not when Outlook downloads it.
Inbox and Outbox Assistant commands are grayed out
The Inbox Assistant and Outbox Assistant features are for Exchange mailboxes only and therefore, work only if you connect to Microsoft Exchange Server.
If you don't have Exchange Server, you'll need to use the Rules Wizard in Microsoft Outlook or check out the alternatives below.
WHat if one has an exchange mailbox and the Out-of-Office is still greyed out? (Outlook 2016 with Exchange 365)
Is this is work account? The admin could have a group policy set that disabled it.
my Outlook/email system is automatically sending an out of office message “vacationmsg” which I have not set up. How do I prevent this?