Modify Out from office / Vacation Siege plugin

[infosxnet]

Hello, i tryed roundcube stable and works awsome. I used the Siege Filters and Rules and wanted to modify the 'Out from office / vacation' plugin. Actually, if user 'a' add this rule, and user 'b' send an email to user 'a', only once 'b' will be notified about. If user 'b' send emails again to 'a', user 'b' will not be notified again.
How can i make that each time user 'b' sends an email to user 'a', user 'b' recieves the message that 'a' is out from the office ?
What should i modify ?
I tryed to look at the code (i'm a python developer) and wasn't easy for me to find where could i modify this functionality.
Thanks in advance,
Emiliano.