Recently I am started seeing eamils landing in my inbox for various signup confirmations for various services which I don't have any idea about.<p>Looks like some spammer using ramdom_name@mygoogleappsdomain.com to signup for services and the signup confirmation emails landing on my catch all google apps admin account email.<p>Should I be worried about this abuse?
As a precaution you should enable MFA for you account and change your password. I would be worried about that someone gained access and is now using the email address to sign up for services etc. If the account was compromised you could also loose your domain quickly if this is the account email for your registration provider and the use it to gain access and transfer the domain.