You have a Lotus Domino Directory Data Source in the Directory Integration Settings for Recipient Validation and see the following errors in the "Directory Data Service Logs:
is not unique. The following entries share the same email address
Errors found in the "Directory Data Service Logs":
The LDAP query used for Recipient Validation is returning multiple records for a single recipient validation query. This is considerd an error as recipient email addresses should be unique to an object in the directory. In the example below recipient validation resulted in multiple returned entries because the "Query filter" is not looking only for the "mail" attribute in the LDAP source but also for "sn" "givenname" and "uid".
Using a ldap browser identify the correct filter to uniquely retrieve the email attribute to validate recipients and substitute that query in the Recipient Validation tab for the data source.
Change the "Query filter" for the Recipient Validation
In order to retrieve the right email attribute to validate recipients
In the following example the "sn" and "givenname" where not matching email attributes but name and surname resulting in multiple records being returned and therefore were removed from the query filter:
RFC 4515 for details on LDAP query filter syntax.