I can't change my E-Mail, it says "invalid Mail" or "Ungültige E-Mail-Adresse"

Hello, I have been trying to change the email address of my EA account for a few days now, but without success. I have already added a secondary email, but I can't remove the primary one. It keeps saying: 'Invalid email address'. And yes, I have already tried five existing emails, and everything is spelled correctly without any spaces or other mistakes.