Mx settings and 123 reg

I have set my domain registrar server settings at 123reg to:
@
MX 10 mx.zoho.com.
@
MX 20 mx2.zoho.com.
@
TXT/SPF v=spf1 include:zoho....

And yet am still having the following error when trying to send/receive email:

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.

admin@hitwiki.site INVALID_ADDRESS, ERROR_CODE :550, ERROR_CODE :sender rejected

Received:from mail.zoho.com by mx.zohomail.com
with SMTP id 1504861530406835.7054347030532; Fri, 8 Sep 2017 02:05:30 -0700 (PDT)
Message-ID:< 15e60bca924.1061cc2be43706.6370600685827065617@hitwiki.site>
Date:Fri, 08 Sep 2017 09:05:30 +0000
From:Paul Farrell < admin@hitwiki.site>
User-Agent:Zoho Mail
To:< admin@hitwiki.site>
Subject:Test
Content-Type:multipart/alternative;
boundary="----=_Part_103210_1268950447.1504861530405"

Can you advise please.