I found out this worked for me.
Use the first part of your email when setting up the "Account Name" for the logging into your POP3 server.
For example:
johndoe@xx.rr.com - just remove the @/domain info and just use
johndoeNow if you use the RR webmail login you have to use the full email address as your user account....but for some reason the Instinct does not require the full email address for login.
Incoming server: pop-server.xx.rr.com (xx represents your local RR settings)
Leave default settings port 110 no ssl
Outgoing server: smtp.sprintpcs.com - do not use the RR SMTP server it only works from their network.
Leave default settings port 25 no ssl
Hope this helps.