ERROR:(EML1001) - java.mail.AuthenticationFailedException 535-5.7.8 Username and Password not accepted
Fig: Error message
This happens when the “Less Secure App” settings is not enabled for your Gmail Account which is configured with DBSync.
Click on the below-mentioned link and enable the “Less Secure App” setting for Gmail Account which is configured with DBSync and then try for the sync.
Fig: Enabling the Less Secure App Settings