iCloud email bounces back but gmail is successfully sent

I had a Google workspace account with multiple custom domain emails. (Godaddy)

I recently deleted my workspace account and setup email forwarding through Godaddy to my new iCloud account. 

Now if I send an email to me@mydomain.com from a gmail account it is correctly forwarded to my new me@icloud.com, but if an email is sent from an iCloud account to me@mydomain.com it is bounced back with this message:

This is a system-generated message to inform you that your email could not

be delivered to one or more recipients. Details of the email and the error are as follows:

Mail Delivery System 

Undelivered Mail Returned to Sender

<me@mydomain.com>: host aspmx.l.google.com[142.250.141.27] said: 550-5.1.1

   The email account that you tried to reach does not exist. Please try

   550-5.1.1 double-checking the recipient's email address for typos or

   550-5.1.1 unnecessary spaces. Learn more at 550 5.1.1

   https://support.google.com/mail/?p=NoSuchUser

   x4-20020a17090a970400b001c6f8962d27si2465783pjo.116 - gsmtp (in reply to

   RCPT TO command)

I don’t understand how sending an email from gmail (or possibly other mail servers) works, but sending from an iCloud account is bounced back by what looks to be Google.

I’m not super familiar with DNS records, but I believe they are setup correctly to perform the email forwarding through Godaddy. Maybe I am missing a record that iCloud (and maybe others) needs. 

Any help is greatly appreciated. 

Thank you.