SMTP/LDAP authenticaion not working

After setting up LDAP authenticaion, IMAP account access from client (Evolution on Ubuntu) works fine, however SMTP does not. I have read through the PAM setup, tried changing the SMTP authenticaion from PAM to LDAP, tried some debugging tools and testing with Telnet. I consistently get the error:

SASL PLAIN authentication failed: generic failure

(If I change my client to LOGIN authentication the word PLAIN changes to LOGIN but everything else is the same.)

Any help would be appreciated.

Thanks