There is no possibility to set the autoresponder replies daily limit per mailbox via Plesk GUI, but one can tune it up inside the psa database
In mail_resp table of psa database you need to modify ans_freq field (equals '1' by default)
To check the set value you can use the following command:
# echo "select ans_freq from mail_resp" | mysql -uadmin -p`cat /etc/psa/.psa.shadow` psa
ans_freq
1