535 Incorrect authentication data + EXIM + cPanel
the solution is below
go to /var/cpanel/serviceauth/
remove the directory exim
cd /var/cpanel/serviceauth/
rm -rf exim
Restart Cpanel.
/etc/rc.d/init.d/cpanel restart
The folder exim will be recreated…
that should fix the issue.
Reference
http://presoon.com/blog/2009/03/20/535-incorrect-authentication-data-exim-cpanel/