question

RudolfAmarlapudi-2729 avatar image
0 Votes"
RudolfAmarlapudi-2729 asked RudolfAmarlapudi-2729 commented

User receives NDR when sending to a particular external email recipient.

Hello,

We are running an Exchange 2016 server (Version 15.1 ‎(Build 2176.2)‎).

One user is experiencing difficulties sending email to an external user. I found that email to this recipient was successful once I deleted the entry from Auto-Fill, and entered it manually. However, when it becomes available again, it keeps bouncing back with the following error further below.

I've also taken the following action:
1. Deleted Auto-Fill entry.
2. Deleted the Contact from the Sender's Contact folder.
3. Created new Outlook profile.


I'm not sure where the point of failure is.

Any suggestions would be greatly welcome.

Thanks in advance.

Regards,
Rudy

Delivery has failed to these recipients or groups:
“Recipient’s Email Address”
The email address you entered couldn't be found. Please check the recipient's email address and try to resend the message. If the problem continues, please contact your email admin.
Diagnostic information for administrators:
Generating server: EXCH2016SERVER.SenderDomain.org
IMCEAEX-_o=NT5_ou=00000000000000000000000000000000_cn=2F9A13C900A8204F882A83FFAFF3595A@SenderDomain.org
Remote Server returned '550 5.1.11 RESOLVER.ADR.ExRecipNotFound; Recipient not found by Exchange Legacy encapsulated email address lookup'
Original message headers:
Received: from EXCH2016SERVER.SenderDomain.org (2002:c001:1dd::c001:1dd) by
EXCH2016SERVER.SenderDomain.org (2002:c001:1dd::c001:1dd) with Microsoft SMTP Server
(version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P384) id
15.1.2176.14; Mon, 21 Jun 2021 10:00:06 -0700
Received: from EXCH2016SERVER.SenderDomain.org ([fe80::f1a1:c5d4:8fb0:2a25]) by
EXCH2016SERVER.SenderDomain.org ([fe80::f1a1:c5d4:8fb0:2a25%12]) with mapi id
15.01.2176.014; Mon, 21 Jun 2021 10:00:06 -0700
Content-Type: application/ms-tnef; name="winmail.dat"
Content-Transfer-Encoding: binary
From: Sender Name<Sender@SenderDomain.org>
To: “Recipient’s Email Address” <Recipient@RecipientDomain.edu>
Subject: email
Thread-Topic: email
Thread-Index: AddmvtJpSP5iLcn6RTW8XY2hs0zkhw==
Date: Mon, 21 Jun 2021 10:00:06 -0700
Message-ID: <5fec2334ee2a48de94b4648642829c33@SenderDomain.org>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator: <5fec2334ee2a48de94b4648642829c33@SenderDomain.org>
MIME-Version: 1.0
X-Originating-IP: [192.168.153.94]
Return-Path: Sender@SenderDomain.org





office-exchange-server-mailflow
· 1
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Hi @RudolfAmarlapudi-2729,
Just checking in to see if above information was helpful. If you have any further updates on this issue, please feel free to post back.

0 Votes 0 ·
JeffYang-MSFT avatar image
0 Votes"
JeffYang-MSFT answered RudolfAmarlapudi-2729 commented

Hi @RudolfAmarlapudi-2729,

Do other users in the same organization have the same issue when using Auto-Fill entry to send emails to the same external user?
To confirm if the issue is related to the Outlook desktop client side, it is suggested for you to try the same operations on your web mail and see if the issue has any difference.

First of all, I would agree with the suggestions michev mentioned above, starting a new thread instead of replying to old emails and avoiding using the auto-complete entry of this user as much as possible should be able to help prevent this issue.

By the way, based on my experience, there is also some cached recipient information which is non-visible and may cause similar issues as well. We could try to delete them using the MFCMAPI tool:

  1. Download and extract the MFCMAPI tool, launch MFCMAPI.exe, click OK, on the Session Menu, click Logon, select the Outlook profile for the mailbox, click OK.

  2. Expand Root Container - Top of Information Store - Contacts - Recipient Cache, right click on it, choose Delete folder, click OK:
    108963-1.png

  3. Exit the MFCMAPI tool and restart your Outlook to test.

Hope these could help.


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Thank you everyone for the feedback. I apologize for the delayed update. I have narrowed down the source of the problem.

I found that this issue was manifesting for multiple external email addresses.

I looked at the Outlook Properties for the Auto-Fill entry. I found that there were additional details including an entry for the Department. I then found that there was an Active Directory account for this external user. I found that these people log on to our Active Directory in order to access some applications. However, they do not use our email system, having their own organizational email. This external email address was defined in the Active Directory account. They do not have a mailbox on our Exchange server.

Even after deleting the Auto-Fill entry, when the new email address was typed in the To: field, it would populate using this Active Directory account.

Taking the following action appears to have addressed the issue.

  1. Removed external email address A.D.

  2. Updated Address Book.

  3. Deleted the Auto-Fill entry.

In some cases, it appeared that this was not sufficient. For these, I added a Contact configured for the external email address. I also created a local mailbox with the local email address. Then, forwarded email to the Contact.

  1. Should an Active Directory account NOT include an external email address if it is being used solely for reference? We also add these users' phone number, for instance.

  2. What then is the Microsoft best pracice in situations like this?

Thanks again.

Regards,
Rudy

0 Votes 0 ·

Here's the AD item I'm talking about.

113971-image.png


0 Votes 0 ·
image.png (30.3 KiB)
JeffYang-MSFT avatar image JeffYang-MSFT RudolfAmarlapudi-2729 ·

Hi @RudolfAmarlapudi-2729,

Thanks for your reply.

I tried a lot of tests in my environment, sending emails to Mail User with external email address and properties like Phone number and Office and so on, emails can still be successfully sent out. So, I'm afraid that the Question1 you mentioned above is not the key of your issue.

According to my search, I noticed that you have already post another thread with the same issue. As Yuki mentioned in that case, the LegacyExchangeDN attribute might lead to similar issues as yours, please try to force generate the LegacyExchangeDN attribute value and if your issue could be resolved.

By the way, in order to further confirm if this send issue is related to specific external email user, it is suggested for you to try to remove and re-create a fresh Mail User using the same external email address to see if there is any difference.

0 Votes 0 ·

Hi Jeff - Thank you and Yuki for the suggestions. It is an odd issue. I'll work on troubleshooting using the feedback I've received from you and Yuki.

I'll close this case for now.

Regards,
Rudy


0 Votes 0 ·
michev avatar image
1 Vote"
michev answered

Is he replying to older emails? Basically ask him to start a new thread, and type in the address without selecting any auto-complete or contact entry.

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