Recurring UserEmailAddressException$MustNotBeDuplicate error importing users with existing emails from LDAP server

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Issue

• There are recurrent UserEmailAddressException$MustNotBeDuplicate errors in the logs when syncing between Liferay and an LDAP server.
• In each sync iteration, in the log are registered errors like this:

  com.liferay.portal.kernel.exception.UserEmailAddressException$MustNotBeDuplicate: User XXXXXX cannot be created because a user with company [e-mail] and email address XXXXXX is already in use

• The errors show the problematic users and their email addresses.

Environment

• Liferay DXP 7.0+

Resolution

• The values of attributes ScreenName and EmailAddress must be unique in the Liferay instance.
• In the sync LDAP process:
  • When a new user is detected in a sync iteration, the user will be imported to Liferay from LDAP.
  • At this moment, the user attributes will be validated.
  • This validation process checks that the ScreenName and Email of the new user are no present in any other existing user. If this happens, a MustNotBeDuplicate exception will be thrown.
  • This is one of the main error causes when importing users.
• If you have this kind of fail, you will have to review the problematic users' attributes and resolve these attribute conflicts to be able to import them.