> Yes, we use stunnel for hiding stuff but don't need to for this

database.

Security is more than simply preventing people from accessing data you
care about. If there is a bug in the engine, than someone may be able
to compromise your entire system.

> Do you think it would be a lot faster via stunnel?

I stunnel offers compression then yes.

> We found that the firebird database server does not respond and I can
> only connect if the Interbase server is running.

What port is Firebird listening to?
Has the RemoteBindAddress been set on the server?
What is your connection string from your client?

Adam