smtp server 5.1 in xp not sending emails

hi iam using asp.net 2.0 with c#.net.
in my application when client completes its shopping email will goes to user this works fine when there is internet connection is working fine,
if  there is some problem  in internet connection if one mail stops then all the mails will be stopped even now internet works fine,
how to resend the emails using smtp server, is there any option to resend the emails automatically when internet works fine.

can you give example which helps me.