delayed: host mx2.zoho.com (136.143.183.44): Network error: Unexpectedly disconnected (STARTTLS)

delayed: host mx2.zoho.com (136.143.183.44): Network error: Unexpectedly disconnected (STARTTLS)

Hi Team, 

I'm not receiving any email. Seems to be an issue. 

Sender sent me the error message they received:

"delayed: host mx2.zoho.com (136.143.183.44): Network error: Unexpectedly disconnected (STARTTLS)"

Please advise.