Here are some steps:
1. Log in to your email address that is linked to your gamesas account.
2. Click the gears icon at the top right of your Gmail page, click mail settings.
3. Click on the Forwarding and POP/IMAP tab, click on Add a new forwarding address and input your email address that you want to use.
4. At this point, Gmail will ask you to verify this forwarding address so it will send an email to the address you inputted with a confirmation code.
5. Sign out of your email, sign into your email that you inputted for a forwarding address in your old Gmail account.
6. Click on the email from Gmail about the Gmail Forwarding Confirmation. Look for the code there and copy and paste it.
7. Sign out from that email and log in to your old email address. Click the gears icon, click on Forwarding and POP/IMAP tab and paste the confirmation code you got in your current email address.
8. Once thats done, leave the Disable forwarding marked as you don't want to forward all your mail, only the gamesas emails.
9. On the Forwarding and POP/IMAP tab, click Create a filter in the tip section below Add a forwarding address.
10. In the from box, put in no-reply@gamesas.com and click Create filter with this search, after the filter has been created, you will be able to forward emails from gamesas. Mark Forward it to: your current email address and click Create filter.
11. Thats it! Any gamesas emails that you receive to your old email account will be forwarded automatically to your new email account.
Like I said, this really should be a temporary solution as really, Crytek should incorporate a change email system in their website. I don't think its a complicated task either as many other websites have this function so Crytek, please make this system available.