ophion
https://docs.grommunio.com/man/gromox.cfg.5.html
Hard to imagine, unless you have any other mechs that break the handling (like not real OOF, but generating new messages all over).
autoreply_silence_window
If an autoreply message (other than a bounce report, e.g. out-of-office) is to be generated, that return message will be suppressed if another autoreply for the given {From, To} address pair was produced within the given time period previously. (Unlike the response_audit_capacity directive, autoreply pairs are stored persistently, in the message database.)
Default: 1day
