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Saturday, December 9, 2017

Exchange - Forward Meeting External Error: 0x80070075

In my environment, we have two Exchange Resource Forests (us.exchangeitup.com and eu.exchangeitup.com) both of which share an Accounts Forest (exchitup.com).

A few of my US users experience Outlook NDRs when forwarding meetings Cross-Forest - from US to EU.

The error thrown is this:

Subject: FW: Meeting
Sent: 12/5/2015 5:50PM


The following recipient(s) cannot be reached:

External User on 12/5/2017 5:50 PM
This message could not be sent. Try sending the message again later, or contact your network administrator. The client operation failed.
Error is [0x80070075-0x80070075-0x00501]


The error is directly from Outlook itself, not Exchange. If you run Message Tracking, you will see that the message was actually sent externally.

The problem I found is, the targetaddress (external forwarding address) does not match any of the external user's proxyaddresses.

**Note** All other forwarding to external mail systems worked fine.

We have an automated provisioning script that creates MailUser accounts in each Resource Forest and then MIM does a DirSync to populate the attributes.

On a few contacts, the primary SMTP address changed (they got married or something), but the targetaddress didn't update. So there was no address in the proxyaddresses that matched the target.

See this example:

Get-Recipient ExternalUser | fl *address*

EmailAddresses                 : {SMTP:external.user@eu.exchangeitup.com}
ExternalEmailAddress       : SMTP:external2.user@eu.exchangeitup.com
PrimarySmtpAddress         : external.user@eu.exchangeitup.com


So, while Exchange does send the message, Outlook can't find a suitable email address in the GAL/OAB for external2.user and throws the error.

To fix this, I added a proxyaddress matching the target:

Get-Recipient ExternalUser | fl *address*

EmailAddresses             : {SMTP:external.user@ue.exchangeitup.com;smtp:external2.user@eu.exchangeitup.com}
ExternalEmailAddress       : SMTP:external2.user@eu.exchangeitup.com
PrimarySmtpAddress         : external.user@eu.exchangeitup.com


Now, no more NDR's!

**Note** The above may not apply to your environment, it's just the solution I found. I have seen this error floating around on the forums that have different scenarios/solutions like emptying the Outlook autocomplete cache, changing to online mode, etc. Those did not work for me

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