I have deleted my old email account as I believed I had migrated everything to my new email, but unfortunately it looks like I have not changed the email address linked to my Steam account.

I no longer have access to my old email address.

I have tried using the credit card form to change my email address, but Steam claims they cannot verify my card (I am 100% sure it is the same card and I have checked that all the information was entered correctly).

After that I had also tried the account information form (basically it asks you to enter the first email address used with the account, payment info, etc.), but Steam claims that the "Captcha" failed and cannot send the request.

I have tried this without using a VPN and it doesn't resolve anything. When last purchasing a game through Steam, I did not have any issues. My problem seems to specifically be tied to the system that handles the email link with an account as both systems in place for changing an email once you've lost access to your old one didn't work. (This is a reply to a comment left on this thread, I cannot post an actual reply because apparently having Steam Guard active is a requirement to post comments).

Basically, I have tried everything I could to change my email to no avail. I need to change my email address as I have to join a Steam family and that requires verification through email.