Hi David, I am not sure how to do so honestly especially if like you said this folder has such an important data that could be used to deter spam.
Since this is production server I want to be very careful in dealing with it and extending the current drive would suffice for me, I can try other options in a lab.
From the terminal I can see that /dev/sda3 is almost full! on the hypervisor I already added 100GB more now I wonder if it's possible to reflect this on the sda3?
It appears deleting these files may destroy all intelligence developed thus far, so intelligence building must start from scratch.
Suggestion: Likely best to open a MailCleaner support ticket + ask their advice.
Also, in your ticket ask them how to use zstd to compress all these files, which for pure text like this... may recover 90%+ of your disk space.