I am sure most of you have used Dynamic send ports at some point in your BizTalk Developer life and more so if you are using the ESB Toolkit.
One of the problems of bottleneck in the Dynamic send ports was it always used to get assosciated with the Default Host instance and there was no way to control the behaviour. So now if you have a lot of Dynamic send ports this becomes a problem.
In BizTalk 2013 now you have the ability to change the send port handler assosciation . The way you do this if you look at the screenshot below is you can now specify which host to assosciate the send port with based on the type of the port.
So now for a port that is using say SMTP for instance you can have a specific host assosciated with the Transport Type. So this now gives you ability to scale in a specific direction.