basic email server question.

i hv a basic email server question...if i configure a linux box to be an email server, then when I send out email from that box does it contact my isp's mail server to send out e-mail or does it resolve the email address on its own? i guess what i'm asking is if i configure a mail server does the isp's smtp server come into the picture at any point?

If I understand your question correctly, it would be its own email server and depend only on the internet infrastucure and the recieving email server only. This is unless you relay your mail through your ISP's email server on purpose.

DNS would still be you ISP's unless you decide to run a external dns yourself.