Can't receive any email from other platform

Can't receive any email from other platform

Hello,everyone, i'm just join zoho and create two email accounts for my own business.
I was using it to get a verified email from stripe, but can't receive it. and I use my private gmail account to send test email twice, first time show below reply, but it is weird,the second one can be received. Im writing email to zohosupport team but still haven't get any reply until now. Does anyone know how to fix the issue?
Thanks 

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  runxu@gupfix.com
    No Such User Here

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