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I recently added AD accounts and email inboxes for three new users in our org. When sending an email to them from within our organization, they arrive without issue. When sending from an external source (such as my personal Gmail account) we get a 550 5.7.1 error. No other mailboxes appear to be having this issue currently, just the ones added earlier today. Other mailboxes have the same domain name as the three having the issue. What might be causing this?

This is on Exchange 2016 and Server 2012

ChickenOverlord
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  • Do you have an interceding mail filtering service? Like, one that performs periodic syncs of the GAL so that mail can be dropped at the connection if sent to an invalid recipient? – Semicolon Apr 25 '18 at 20:30
  • And frankly - if you do - it should not be returning the NDR. It is potentially creating a lot of back-scatter, and is aiding those who perform Directory Harvest Attacks. – Semicolon Apr 25 '18 at 20:31

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First Test inbound SMTP https://testconnectivity.microsoft.com/ & post the results.

Mostly occur due to the domain was changed from .com to .local

Use Command:

Get-ReceiveConnector “relay” | Add-ADPermission -User “NT AUTHORITY\ANONYMOUS LOGON” -ExtendedRights “ms-Exch-SMTP-Accept-Any-Recipient”

relay = name of your connector.

Check out the links for more info Link and Link1

Robinsan shaw
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