Unable to Receive Emails on Zoho Mail After Office 365 Coexistence Setup – Error: 553 Relaying Disallowed

Unable to Receive Emails on Zoho Mail After Office 365 Coexistence Setup – Error: 553 Relaying Disallowed

Hello,

My domain name is bigniter.com, and I’ve been using Zoho Mail as my email service provider without any issues.

Recently, I followed the steps outlined in the Zoho documentation to enable Coexistence with Office 365:
🔗
https://www.zoho.com/mail/help/adminconsole/coexistence-with-office365.html#multi-server

The configuration was completed successfully. However, after setting this up, I’m unable to send emails from my personal Gmail account to my Zoho email address.

The bounce-back error I receive is:

550 5.0.350 Remote server returned an error -> 553 Relaying disallowed

It seems to be a relaying issue, possibly due to the coexistence configuration or routing settings.

For your reference, I’ve also included:

  • My current MX records

  • SPF record

  • Full email header

I would appreciate your help in resolving this issue.

Thank you,