@ethar is that a trashed record; because while your validation rule explicitly excludes soft-deleted records, the database's UNIQUE index is ignorant of soft-deletes as a concept!
@ethar well, that depends on the business logic; but it seems you want the trashed record and a new one with the same mobile, so UNIQUE might not be appropriate on the database, but can still be enforced with validation rule.
@ethar Generally I think this is a bad idea. Because when you restore that soft delete (which is surely the idea behind using soft deletes - the fact that you can restore the record if you need to), you're going to end up with two records that have the same value.
For storing/adding record in database
'email' => 'required|email|unique:users,email,NULL,id,deleted_at,NULL',
For updating/editing record in database
'email' => 'required|email|unique:users,email,'.$id.',id,deleted_at,NULL',
Here $id is record id of particular editing user in user table.