[Help] Hamachi Connection

As the title says, im using Hamachi to try and get people to connect to my WOTLK 3.0.9 server [ArcEmu].
but the problem is, one of my testers [the only one currently] cannot connect, but I can.
He can connect to other servers so its not his WoW.
So i was wondering, what do i need to do so other people can connect to my server?
And yes, his realmlist is set up to connect to my server.
Please help, it would be greatly appreciated.

For all people with connection problems;

Please, post your emulator revision and configurations in your posts, otherwise we cannot help you besides doing a simple guess.

Note: Be careful with passwords and adresses in your configs!