Registration Problems - creating new users

I have encountered strange issue (problem) while creating new users.

Description:
1.I have created user – it was me and I made myself administrator from the admin section.
2.Later I have deleted this user again from the admin section.
3.After this when I wanted to create the user again (same name, address) using the same e-mail address as the first time I have received the message: "The e-mail address that you entered is already in use. Please enter a different e-mail address."
4.I have cleared the cache from the Administration section, but still have the same problem.
5.I am also unable to see way in My Account to change the primary e-mail address of any user – if for example somebody needs to change their primary e-mail used during their first registration.

Do you have any idea what is the problem?

Actually customer is not deleted when you click "delete customer" in admin area. He is only marked as deleted. That's why you receive the message "The e-mail address that you entered is already in use. Please enter a different e-mail address".

Thank you very much for this clarification.

Just two questions:
1. Is there any way to really delete the customer?
2. Is there any method for the customer to change the primary e-mail address he has used during his first registration?

1. You can manually delete it (from database)
2. You can change e-mail address only if "Login/registration by usernames" is enabled

Presuming the manual deletion, I have tried to search (query) for the user (SQL Server Management Studio) but there is no record for him. I presume that he is somewhere stored in different way or something - very strange.

What is your advice for the so called manual deletion from the database when I am not able to find them? You have said that they are marked as deleted, but not actually deleted from database.

Look at [Nop_Customer] table

I am curious why the customer is not deleted from the database when they are deleted from the admin section.  I have noticed the same is true for products.  The database will continually increase in size causing space issues for some.  Could you please explain?
Thank you in advance.

from topic https://www.nopcommerce.com/boards/topic.aspx?topicid=3466

there is a good reason for not physically deleting the record from the DB. suppose you had a product that was sold on your site and is not available anymore or you dont carry anymore.

if you look at historical data and want to see the order details of one or more customers who bought it, if the product does not exist in the db anymore, you would have errors and a lot of data inconsistencies.

Why not keep the row(s) in the db. Change the email field in the appropriate table(s) with "[email protected]”? I have done so and it hasn’t been a problem for me.

Please can you give me scrpit to delete all the customers?