Long, confusing story as to why this happened. I'll give the short version. Couple hundred contacts were imported into AD as mail enabled contacts. Those were then DELETED. Client is now reporting that they are not able to send emails to anyone that was imported and then removed. Message received as follows: Diagnostic information for administrators: Generating server: EXCHANGE.LOCALDOMAIN.local IMCEAEX-_O=FIRST+20ORGANIZATION_OU=EXCHANGE+20ADMINISTRATIVE+20GROUP+20+28FYDIBOHF23SPDLT+29_CN=RECIPIENTS_CN=DESTINATION@LOCALDOMAIN.com #550 5.1.1 RESOLVER.ADR.ExRecipNotFound; not found ## Original message headers: Received: from EXCHANGE.LOCALDOMAIN.local ([::1]) by exchange.LOCALDOMAIN.local ([::1]) with mapi; Tue, 25 Jan 2011 15:12:33 -0500 Content-Type: application/ms-tnef; name="winmail.dat" Content-Transfer-Encoding: binary From: SENDER <SENDER@LOCALDOMAIN.COM > To: DESTINATION <DESTINATION@EXTERNDOMAIN.COM > Subject: FW: XXX Thread-Topic: XXX Thread-Index: XXX Date: Tue, 25 Jan 2011 15:12:32 -0500 Message-ID: <XXX@exchange.LOCALDOMAIN.local> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: yes X-MS-TNEF-Correlator: <XXX@exchange.LOCALDOMAIN.local> MIME-Version: 1.0 I did a little digging, forced an OAB replication and then updated the clients OAB in her outlook with no success. Tried removing the contact in question from her n2k file and that didn't help either. Other clients are reporting that if they have the email in their outlook contacts than the mail goes through. Rather stumped. Any help would be appreciated.

I have found that if we turn "Cached Mode" in the clients outlook off they are able to send the email without problems. Looks like this is an OAB problem. Will the removed address eventually be removed from the OAB?

When you say you forced an OAB replication, what exactly did you do? OAB generation can take some time, depending on the number of objects in the GAL. get-offlineaddressbook | update-offlineaddressbook That will force the OAB to regenerate. Then you need to wait for the process to complete. Finally you can download the updated OAB. However the OAB generates automatically every night, so given the original question is almost 24 hours old, there is a good chance that the OAB has already updated. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources

Yeah I used the get-offlineaddressbook | update-offlineaddressbook. But I probably didn't wait long enough for it to regen. I haven't heard from anyone that they're not able to send emails today so hopefully it should go through without a problem. Thanks much for the response.