Unfortunately, I think that your original message is not too clear. Tell me if I understand it correctly.
You have created a filter in roundcube to send a ‘vacation’ message but it only sends a reply message to domains which are located within MaiB, but not in reply to emails received from other email providers? Do I understand correctly?
Would you please be more specific with the comment:
I did a test, and set up a vacation filter and it worked fine sending a vacation reply to an incoming message from an email account on one of my local domains as well as an incoming email message from a protonmail.com account. So, I can only suggest that you double check to be certain that the filter was set up correctly, and was enabled.