Error Code 554

Hi Team,

I am receiving the following error message when trying to email our supplier. This has only happened today.

INVALID_ADDRESS, ERROR_CODE :554, ERROR_CODE :Service unavailable; Client host [sender154-mail.zoho.com] blocked by dnsbl.sorbs.net; Currently Sending Spam See: http://www.sorbs.net/lookup.shtml?74.201.84.154

Can you please let me know if this is being blocked by Zoho?

Cheers,

Lauren