vacation ooo out of office

Important: To have OoO up and running, I-MATH Zimbra users have to setup OoO three times!
on Zimbra as described below
on Outlook as described below
on Outlook even for 'Send replies outside of your organization'
Zimbra
Log onto the webmail interface mail.math.uzh.ch
Go to 
Preferences > Mail > (scroll the big right window down) Receiving Messages > When a message arrives: Send auto-reply message: ...
Press 
Save
Please be aware: Notifications will only be sent once a week per person. This means, if you send a testmail to yourself on Monday, you will receive the automatic reply. If you send a second testmail to yourself 5 days later, you will not!
outlook.com
https://support.microsoft.com/en-us/office/set-up-auto-reply-out-of-office-cc0e480f-973e-4412-a27b-8a52108d6d51
Take care that you put your OoO message two times in the 'automatic reply'-Settings:
Send automatic replies inside your organization
Send replies outside of your organization