mail's gotten more and more "auto setup" over the years. Outgoing is going to be a bugger anyway though.
MOST isps do NOT allow you to use their SMTP server unless you are on their network. And most don't require authentication. AND many actually block you from using anyone else's unauthenticated smtp server. (to disable spambots that get loose on their network)
So you are most likely going to have to send mail using your new ISP's smtp server.
NOTE: some isp smtp servers will not allow you to specify a different address other than yours in the "From" or "reply-to" fields, which basically makes the whole exercise pointless.
