Help save my hair!

I have recently installed emclient free version on my laptop (Windows 7) and can receive email but cannot send messages. Error message - “server says #5.7.0 authentication failed” then “invalid character in Base-64 string”. I have checked password, user name & email address and all are correct. Any ideas on how to fix this? My ISP is Talk Talk (taken over my Pipex account).
This is very frustrating.
Douglas Barnes

Problem solved by emclient diagnostic tool. Email working OK now and hair is regrowing!