I use GoDaddy for email hosting, and all emails sent to my Zendesk are suspended. Why?
When an external support address is set up to forward to Zendesk through GoDaddy, there is an option to set up forwarding to additional recipients in addition to Zendesk.
When forwarding is set up to multiple recipients, GoDaddy adds the email header
Precedence: bulk to every email that is sent to Zendesk. This results in Zendesk suspending all of these emails as automated responses.
Precedence: bulkemail header.