Environment forest1: Exchange 2013, Active directory level 2008, Clients running Office 2007, 2010 and 2013. Environment forest2: Exchange 2013

In forest1 there were some exchange contacts of forest2 because there is no trust relationship between them, everything is separate. Until yesterday everything went fine with sending mails between the two forests until I deleted the Exchange contacts (in forest1) through Active Directory Users and Computers console and re-created them there. Since then when I type the name of a contact in the To: field of outlook (in forest1) and complete it by pressing Ctrl-K and send the mail after a few seconds I get a message back from the exchange server in forest1 with the following message:

Delivery has failed to these recipients or groups:

(Contact's name in forest2)

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 helpdesk.

Diagnostic information for administrators: Generating server: SERVER36.forest1.com

IMCEAEX-_o=BE+20Group_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=ContactsName@forest1.com Remote Server returned '550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found'

Original message headers:

Received: from SERVER36.forest1.com ( by Server36.forest1.com ( with Microsoft SMTP Server (TLS) id 15.0.1210.3; Wed, 14 Jun 2017 07:30:11 +0300

Received: from SERVER36.forest1.com ([fe80::9576:69c7:7ea0:5847]) by Server36.forest1.com ([fe80::9576:69c7:7ea0:5847%12]) with mapi id 15.00.1210.000; Wed, 14 Jun 2017 07:30:11 +0300

Content-Type: application/ms-tnef; name="winmail.dat"

Content-Transfer-Encoding: binary

From: (My name)

To: (Contact's name)

Subject: Test

Thread-Topic: Test

Thread-Index: AdLkxuj2VLtvJxLWQIysabpAG53HzA==

Date: Wed, 14 Jun 2017 07:30:11 +0300

Message-ID: <288fb653e30145b4818e5ca3d7914cdb@Server36.forest1.com>

Accept-Language: en-US, he-IL

Content-Language: en-US

X-MS-Has-Attach: yes

X-MS-TNEF-Correlator: <288fb653e30145b4818e5ca3d7914cdb@Server36.forest1.com>

MIME-Version: 1.0

X-MS-Exchange-Transport-FromEntityHeader: Hosted

X-Originating-IP: []

Return-Path: myName@forest1.com

X-KSE-ServerInfo: Server36.forest1.com, 9

X-KSE-AntiSpam-Interceptor-Info: internally-submitted e-mail

X-KSE-AttachmentFiltering-Interceptor-Info: protection disabled

X-KSE-Antivirus-Interceptor-Info: scan successful

X-KSE-Antivirus-Info: Clean, bases: 14/06/2017 00:53:00

Unfortunately I couldn't find any help on google for this issue. Things I've tried to do:

  • Sending from OWA from forest1 to the same contact works
  • Sending from phone from the same mailbox works
  • I re-downloaded the offline Address book to outlook
  • Problem occurs when sending from Outlook 2007, 2010 and 2016 (2013 not tested)
  • Cleared the Cache from Auto-Complete List
  • After typing the name of the recipient of forest2 and hovering with the mouse over it, it indeed shows the right email address, also in the mail returned from my exchange server it shows the right mail address.
  • Sending mails from forest2 to forest1 is unaffected.
  • I deleted all the contacts in the Active Directory but still the problem exists. Also re-created the contacts in Exchange - no difference.
  • Rebooted the exchange server - no difference

As I couldn't find much help yet I ask you if maybe one of you guys have experienced something like this in the past or has a guess what the cause or the solution might be (and please don't tell me to work just with OWA from now on :-))

Thank you

  • Are the contacts from forest1 and forest2 in the same maildomain, e.g. @example.com? Or do they have different domains? – Lenniey Jun 14 '17 at 7:16
  • Also: check your security settings in the contacts on forest2, maybe you got something set there you forgot on forest1. – Lenniey Jun 14 '17 at 7:26
  • If it was the security settings it wouldn't work in OWA and on the phone. The contact objects are saved in forest1 and pointing to user's email addresses in forest2 – josibu Jun 14 '17 at 12:50

OWA and Mobile works, it means no problem with the address list or the contacts themselves. The issue would be the Address Book in Outlook related.

By default, OAB will be updated on Exchange Mailbox server every 24 hours. You can try: 1.Remove the contacts from auto-complete list; 2.Change Outlook from cache mode to online mode; 3.Try to input the full email address. Then you would be able to send the email out successfully.

  • As mentioned in the first post, Options -> Mail -> Empty Auto-Complete List does not help. When I paste the full mail address into the To: field and in the same moment click on send, in the second, Send is pressed it changes the User's address entered to the user's name. What work indeed is switching to online mode. But since some of the computers are laptops this is not a suitable solution. When I change back to cached mode, sending fails again. Any other guess? – josibu Jun 14 '17 at 12:55
  • What really made me thinking is the line IMCEAEX-_o=BE+20Group_ou=Exchange+20Administrative+20Group+20+28FYDIBOHF23SPDLT+29_cn=Recipients_cn=ContactsName@forest1.com The targeted address is in forest2. But the CN says ContactsName@forest1.com. Mustn't it say something about forest2? – josibu Jun 14 '17 at 12:57
  • By default, a contact will get an email address from the default domain of the Exchange org they are created in, so nothing there to be concerned about. – Sembee Jun 14 '17 at 19:23
  • But it should point to forest2.com because there is no mailbox for that user in forest1 – josibu Jun 14 '17 at 19:25
  • Nothing to do with mailboxes. By default all objects in Exchange get an email address in the default domain - even contacts. So you may have added an additional email address. (It is also sneaky trick to give an external personal an internal email address without giving them a mailbox). The fact that you are getting the long NDR with the default domain on it is probably Exchange adding it because it cannot find the original object - because you deleted it. See my answer below about the OAB. – Sembee Jun 14 '17 at 19:28

Standard tests - does it work from OWA? If so, then the issue is the OAB or nicknames. Nothing else it can be. OWA is live information from the domain.

The OAB is updated once a day by default, but due to the way Outlook works it can take up to 48 hours before the change is seen automatically within the client.

The fact that it works in live but not in cached with Outlook also points to the OAB.

Now if the OAB is still failing after that window to present updated information, then you have a bigger problem.

Find a machine with the issue, shutdown Outlook and delete the *.oab files. Then open Outlook. Wait five minutes or so and check again - making sure you select the address from the Address Book and not any popup list. The act of deleting the OAB files forces a full download of the OAB rather than an incremental file. It if works from that point then the OAB incremental files are not updating. If it still fails, then your OAB has stopped updating correctly.


So I found a solution. I came across this thread where Matt5639 says not always it is enough to just re-sync the OAB but recommends to just delete the OAB files located under %AppData%\Local\Microsoft\Outlook\Offline Address Books. I also ran a few commands from exchange management shell:

Get-GlobalAddressList | update-GlobalAdressList

Get-AddressList | update-AddressList

Get-OfflineAddressBook | Update-OfflineAddressBook Either of them did the trick. Thanks

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