This is the query:
SELECT lower(email) email, id, username
FROM mantis_user_table
WHERE lower(email) IN (
SELECT email
FROM (
SELECT lower(email) email, COUNT()
FROM mantis_user_table
GROUP BY lower(email) HAVING COUNT() > 1
) tmp
)
ORDER BY lower(email), username

The purpose of this query is to identify users with duplicate email addresses. I have tested it with MySQL and PostgreSQL, but unfortunately I do not have access to an SQL server instance so I couldn't confirm for that platform.

I guess that adding AS mycount after SELECT lower(email) email, COUNT(*) should do the trick. You can test this by running the query directly against your database, or in context by editing user_api.php at line 334.

Please confirm if that solves the problem, and if not maybe you can help by providing a query that works on MSSQL.

Perfect !
thank you so much

PR https://github.com/mantisbt/mantisbt/pull/1947