I cannot log in because the security code has not been sent to my registered e-mail address.

Thank you. I have contacted AOL support. This was their reply:

The domain extension is the ".com" part of your email address. While most AOL accounts end in "@aol.com", some older accounts may have a different extension depending on where they were created.

Please note that an email address can have different extensions, such as @aol.com or @aol.de. Regardless of the extension, it is the same email address and no other email address can be created with the same username. In your specific case, ******@aol.com and ******@aol.de are the same e-mail address (only with different extensions).

Only accounts with the AOL domain "@aol.com" can be created.

If you have an AOL ID with a different local domain, e.g. "@aol.de" or "@aol.fr", make sure you enter the correct domain extension when entering your email address. If an email is sent to the wrong domain, it will not be delivered.

To check which extensions are available for your email address, you should open AOL Mail in a browser such as Chrome or Internet Explorer, click on the Write button in the left-hand corner of your screen and then click on the small arrow next to your email address and display name. This will populate a menu showing all available extensions.

If the domain extension you want to use is not listed there, unfortunately it is not available for your AOL screen name.

We hope this information will help you.