Different NDRs from 365

[TheRealJMartinez]

I have a tenant with 365. When I sent an email to an invalid recipient, 365 responds with:

Remote Server returned '554 5.4.1 <test-org.mail.protection.outlook.com #5.4.1 smtp; 550 5.4.1 Recipient address rejected: Access denied. AS(20xx0xxx) [BN8xxxxxFT049.eop-NAM04.prod.protection.outlook.com]>'

However, with another tenant on 365, when I send an email to an invalid recipient, I get a really handy NDR with great information for the end user saying "The recipient isn't found". In fact, they get a different error code 550.5.1.1.

My question is, why doesn't my 365 send out those helpful kinds of NDRs for people who send emails to invalid addresses in 365?

[#2 · Accepted solution]

Hello,

This might be DBEB

https://docs.microsoft.com/en-us/exchange/mail-flow-best-practices/use-directory-based-edge-blocking

https://techcommunity.microsoft.com/t5/exchange-team-blog/in-deployment-directory-based-edge-blockin...

[#3]

Thanks Andres. That sounds like exactly what it is. Any idea why I receive enhanced NDR from some 365 customers and not from others?

[#4]

Probably because, a different component rejecting the message depending on DBEB enabled or not

[#5]

@AndresGorzelany Thank you for your assistance.