It's true that you can change your email address in your settings on the Community. However, that change will revert the next time you login, if you have a Webkey and that Webkey has a different email. To update the Webkey email, you can use this link: https://www2.industrysoftware.automation.siemens.com/webkey/update.jsp
If your account here is tied to a Webkey, it will always use the Webkey email address. That's why it seems like it doesn't work.
The page does exist, but I guess direct linking to it doesn't work right. Sorry about that. You can visit https://www2.industrysoftware.automation.siemens.com/webkey/ and click "Update", as someone posted above.
Now it is good, thank you Katie, unfortunately, for my case , to modify my e-mail address , i need to change "WAC/LM Host ID" and i can't , i lost it