What do you mean by "server name" ?
For instance, an internal fileserver might have 2:
Netbios name = fileserver
FQDN = fileserver.mydomain.local
Test 'em both. Also , use nslookup on VPN client to check how both names resolve against internal DNS server.
DNS should be able to handle FQDN, to handle netbios names, you might configure dns suffix for vpn users