Issue deleting Mailbox

If we take a closer look at the error message, it is about the following message:
Access is denied. Active directory response: 00000005: SecErr: DSID-03152501, problem 4003 (INSUFF_ACCESS_RIGHTS), data 0

This error message can be interpreted to indicate that there is an authorization problem and the mailbox/active directory account cannot be deleted.
In most cases this problem can be solved relatively easily. First of all you have to check which permissions were given to the user. Should this user be Domain Admin, Enterprise Admin, etc. Should these permissions be removed in a first step.

In a second step there is usually a problem with the inheritance of permissions. To be able to view and edit them we need to display the Advanced Features in the Active Directory Users and Computers:

Then we browse to the relevant user and open the properties:

On the Security tab we click on “Advanced”:

Here we click on” Enable inheritance” and confirm this with “Apply”:

Afterwards we get a warning regarding the inheritance.

Press “Yes”

Switch back to the Exchange Management: https://maillogon.dk/ecp and delete the mailbox.