su - zimbra
zmprov ma
user@domain.com zimbraPrefOutOfOfficeCacheDuration 1d
You could also modify it on a COS:
zmprov mc cosName zimbraPrefOutOfOfficeCacheDuration 1d
This is now also available in the admin console of newer 5.0.x versions > user or COS preferences tab > out of office cache lifetime.
Only 1 away message is sent per incoming message address over that specified time.
Thus duplicate away messages will not be sent to the same user in the given interval of x time. After that time expires, if they send that account an email, they would again get back another notification.
Setting to 0 would send an out-of-office notification in response to every email received from an address - but the feature is nice afterall.
Plus, if you have user A with an away message up, user B sends an email, and immediately puts up their away message (with the attribute set to 0) you could technically get a loop. You can do hours, minutes, & seconds as well, but seconds especially probably isn't useful.
I prefer 3d or every week 5/7d depending upon how long the user is gone. ie: If they're typically gone a month, then every week.
The other attributes:
zimbraPrefOutOfOfficeDirectAddress
zimbraPrefOutOfOfficeReply
zimbraPrefOutOfOfficeReplyEnabled
zimbraPrefOutOfOfficeFromDate
zimbraPrefOutOfOfficeUntilDate