Get Redmine user details by user email id

Is there any redmine REST API available for company admin to get the details of user by giving users email id.

details like redmine KEY etc

Yes there is, you can do what you want in 2 API requests:

1) http://your-redmine-url/users.json?name=user@email.com

Using this request you will get basic details for user with email user@email.com

2) http://your-redmine-url/users/193.json?include=memberships,groups

Using this request you will get additional details for user with ID 193 (which we got from previous request) like user's API key, status etc.

Also note the following:

• you need to use account with admin privileges to get these additional details
• user's API key is only available through API starting from Redmine 2.3.0
• user's status is only available through API starting from Redmine 2.4.0

All this info is from Redmine docs, which you can find here.