question

Sehwag-5088 avatar image
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Sehwag-5088 asked joyceshen-MSFT commented

Query pertaining to sub domain

Hi Team,

Hope you are doing good.

I have an office 365 domain that i have verified/added and DNS records published, Consider this Domain to be Contoso.com

I have added a subdomain in office 365,lets call it xyz.contoso.com, though I have not published any office 365 DNS record for the same in DNS registrar.

I created a user keeping Primary SMTP with @contoso.com and created an alias of the same user with @xyz.contoso.com

When an external user addresses an email at @xyz.contoso.com, mail gets successfully delivered/received.

How is DNS query working here when I have not created any DNS record in this regard for this domain?

Another scenario is, when i change primary smtp to @xyz.contoso.com and address an email to the same, mail delivery fails, why?

Please help me in understanding this.


Thanks,
Harshit Malhotra

office-exchange-online-itprooffice-exchange-server-mailflow
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Hi @Sehwag-5088

Is there any update about your issue?

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AndyDavid avatar image
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AndyDavid answered

Sounds to me like the sender is resolving the proxy address on the client side.
or an A record exists for xyz.contoso.com

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joyceshen-MSFT avatar image
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joyceshen-MSFT answered

Hi @Sehwag-5088

Is your environment cloud-only or you are having a hybrid? Could you please provide more information how you configured the DNS records(include A,MX,CNAME...) for your primary domain and subdomain?

Could you please share the NDR message you received when failed sending message to the address? Have you checked the message trace log to get more information?


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