Welcome to the forums,
Did zimbraPrefOutOfOfficeCacheDuration somehow get set to 0? Which would send an out-of-office notification in response to every email received. (Default is 7 days.)
Intended functionally: Duplicate away messages will not be sent to the same user in the given interval of x days. On day x+1, if they send that account an email, they would again get back another notification.
CLI:
zmprov gc COSname | grep OutOfOffice
zmprov mc COSname zimbraPrefOutOfOfficeCacheDuration 7d
and:
zmprov ga
user@domain.com | grep OutOfOffice
zmprov ma
user@domain.com zimbraPrefOutOfOfficeCacheDuration 7d
Don't forget to update your profile with version info (Assuming 7.1.0 since you just downloaded.)