You can search for users with email MFA using the query string pattern in either the Admin UI search bar or via the Search API:

twoFactor.methods.method:email

This follows the same pattern used for searching users by any MFA method.

Getting an Accurate Count Efficiently

To get a count without retrieving all user records, use the Search API with accurateTotal enabled and a minimal numberOfResults:

{
  "search": {
    "accurateTotal": true,
    "queryString": "twoFactor.methods.method:email",
    "numberOfResults": 1,
    "startRow": 0
  }
}

The response will include a total field containing the exact count of matching users.

Last-Used MFA Information

Unfortunately, FusionAuth does not store a timestamp for when a user last used their MFA method. However, each MFA method object includes a lastUsed boolean field at users[x].twoFactor.methods[x].lastUsed that indicates which method was most recently used by that user. This is a boolean flag rather than a timestamp, so you can identify which method was used last but not when it was used.