If you can not remember your password any more, please use the "Lost password?" feature:
https://login.domaindiscount24.com/support/password-reset
Here you have to provide your email address on file and your 8-digit customer id.
Your e-mail-address on file is that one where e. g. all invoices have been sent to by our system.
Your customer id is part of the subject of most of the e-mails received from Domaindiscount24.