Scan ftp under hostname not work

Customer use bizhub 211 scan ftp to computer
Customer use network auto ip
1. We configured ftp with ip of computer, It scan work . But ip will change every time when the computers is turned off and turned on, Because customer use network auto ip
2. We will solve the problem configured ftp with hostname But it can not be scanned.
why use hostname it not work
How to configured.

Thank you