There seems to have been some confusion generated by readers trying to implement dynamic direct bound ports that I wanted to clarify. A dynamic direct bound port is merely a direct bound port whose address is set at runtime. It is not a dynamic send port. Dynamic send ports allow you to determine at runtime which send adapter the message will be routed to which is derived from the prefix of the address of the endpoint you have provided. If you try to set the address of a dynamic send port using the msgbox: prefix you will get a routing exception (transport cannot be resolved) as msgbox: is not an alias for any send adapter.
The ability to modify the address of a direct bound port is only available in BizTalk Server 2006.