I was trying to send a mail from hosted domain when I got this NDR

<<..
Technical details of permanent failure:
PERM_FAILURE: Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 554 554 Service unavailable; Client host [72.14.204.233] blocked using dnsbl.sorbs.net; Currently Sending Spam See: http://www.sorbs.net/lookup.shtml?72.14.204.233 / Spam Received Recently See: http://www.sorbs.net/lookup.shtml?72.14.204.233 (state 14).
..>>

IP: 72.14.204.233 belongs to Google and is used for email server of hosted domains :)
I'm not sure how serious is sobrs.net list but atleast someone is rejecting mails banking on this.

I hope Google knows this and are taking care of it.