I have server on ip XXX.XX.XXX.XX
In digitalocean control panel i have floating ip ZZZ.ZZ.ZZZ.ZZZ

Apache works correctly, so i can see website on ZZZ.ZZ.ZZZ.ZZZ
MySql works correctly for localhost

I want to setup remote connection to mysql

if i write in terminal

root@SERVERNAME:/# host XXX.XX.XXX.XX
XXX.XX.XXX.XX.in-addr.arpa domain name pointer SERVERNAME.
XXX.XX.XXX.XX.in-addr.arpa domain name pointer SERVERNAME.local.

but if

root@SERVERNAME:/etc/mysql# host ZZZ.ZZ.ZZZ.ZZZ
Host ZZZ.ZZ.ZZZ.ZZZ.in-addr.arpa. not found: 3(NXDOMAIN)

in mysql config files i tries a lot of bind-address, like XXX.XX.XXX.XX, 0.0.0.0 and * or ::
If i write ZZZ.ZZ.ZZZ.ZZZ in config, mysql refuses starting