[exim] Isp uses ASMTP

Hi i have this router below to catch any email sent to Aol
It sends them via my ISP's smtp server

send_to_smart_host:
driver = manualroute
route_list = aol.com relay.plus.net
transport = remote_smtp

Its works a treat at the moment. But in the future i may have to use a
similar setup for other customers. My question is if there ISP used
ASMTP how would
i include the user name and password in thee above router?. In other
words if relay.plus.net needed a username and password.
I'm sure ive seen it some where on the list but failed to find it.

Cheers Terry