Unable to receive external inbound email

[ngoug]

I Have zimbra 8.8.10 collaboration network, and configure Exchange Online Protection(EOP).

When sending an external mail, i get the undelibery mail below :
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This is the mail system at host btl-rds02.labex.local.

I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can delete your own text from the attached returned message.

The mail system

<sec2@secmail.dns-cloud.net>: Host or domain name not found. Name service error
for name=btl-rds02.labex.local type=A: Host not found
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btl-rds02.labex.local is the local zimbra server name
secmail.dns-cloud.net is the public DNS name zone


Needs your help .

[DualBoot]

Hello,
Your Zimbra is unable to resolve secmail.dns-cloud.net

Regards,