When adding an external file server to the IMP, the External File Server Public Key has a limited number of characters and cannot be fully entered into the CentOS Public Key.
The file server is CentOS8.
[root@localhost mftuser]# ssh-keyscan -t rsa 172.16.100.204
# 172.16.100.204:22 SSH-2.0-OpenSSH_8.0
172.16.100.204 ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABgQDisjG7hgKGB2fkVJl1c1mnAHclkO5+vWqIijBzq9fFbxad3vdT/moijoG7KdZRwHY7idfWkShX9EngTFQMS7+zTrjhHN28ZPGfC8GiImqv1C+X/1mQ8fhoqd+ET4H0AzX/Ro902VfZfIsgYarTujacfx5iWXIUtXnby2khCjrUV5o7TMOiaiJ90YKmuZYRfF2n/aIFYTmfP4lSdbzMs1Tcye4ps17jB7b384a9LdYYoR9oaIm9Q/GdXs0DO64TsCNlYcWROaHXdFLO+rfqraROzIcEzzYS4SAz928IU+FsEjZGhMNgaja59//DUKCAsf9nv+6RiDlexz0WPWhIBmvfpNehFZLkgyTp4wPMIea/jHWSzP8qGNI19kXlJ7/t/I8y2Dj53ifqXSMgg6jqOg+ivdzqlVI7YRu3Cg6YzmU=
Bold cannot be entered.