Have you tried entering the imap info for the smtp server and select my outgoing server requires authentication and using the same username and password? Also smtp.sprintpcs.com reguires you to change the port from 25 to 24 and use your Powervision username and password for authentication. If none of this works here is a link to a list of tons of free smtp servers you can try
http://www.e-eeasy.com/SMTPServerList.aspx