Many of my outbound mails don't get delivered I get the following response from Zoho. See below. Can anybody help please.

Thanks

Hans 

This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. 

elizabethgordon@btinternet.com , ERROR_CODE :421, ERROR_CODE :4.7.0 Temporarily Deferred



Received:from macbook-air-van-hans.fritz.box ( a83-162-185-55.adsl.xs4all.nl  [83.162.185.55]) by  mx.zohomail.com
with SMTPS id 1473941208886212.41640216985957; Thu, 15 Sep 2016 05:06:48 -0700 (PDT)
Message-ID:< 9EE27DD0-20AF-423B-B8C6-883CB70C8B74@vandenhooff.com >
Date:Thu, 15 Sep 2016 14:06:45 +0200
From:Hans van den Hooff < hans@vandenhooff.com >
To:Liz Gordon < elizabethgordon@btinternet.com >
Subject:Re: Ken Blanton: Reader's Report
Content-Type:multipart/alternative; boundary="Apple-Mail=_68B52435-6E67-4582-9137-403D8C74C91E"