[exim] port/helo expansion in transports

In smtp transport I am setting port/helo_data dynamic from a extract
from $acl_c_* .. How will this behave? Will exim still try to transport
other messages (where port/helo_data is different) over the same
connection?

If this will not work the way I hope, what options do I have for
accomplishing this?

--
Bj(/)rnar