Smtp;550 5.1.1 RESOLVER.ADR.RecipNotFound; not found

Question

hello All,
I am getting the above error when i send a mail from external domain. I have exchange server 2010 on and O365 account. From last 2 months i am not using O365 account and even active sync is also not working. And recently O365 subscription was over. So now
non -synced users are not getting mails from external domain. Please find the below complete error.
The email address you specified couldn't be found or is invalid. It may be due to a bad entry in your Outlook or Outlook Web App recipient AutoComplete cache. Use the steps below to delete the entry from the cache:
Click New mail.
In the To field start typing the recipient's name or email address until the recipient appears in the drop-down list.
Use the DOWN ARROW and UP ARROW keys to select the recipient, and then press the DELETE key.
Then resend your message – delete and retype the recipient’s name or e-mail address before sending it.
For more tips on how to resolve this issue see DSN code 5.1.1 in Exchange Online.
Diagnostic information for administrators:
Generating server: DM2PR08MB368.namprd08.prod.outlook.com
[email protected]
Remote Server returned '550 5.1.1 RESOLVER.ADR.RecipNotFound; not found'
Original message headers:
Received: from BLUPR08CA0072.namprd08.prod.outlook.com (10.141.200.52) by
 DM2PR08MB368.namprd08.prod.outlook.com (10.141.55.154) with Microsoft SMTP
 Server (TLS) id 15.0.1010.18; Wed, 20 Aug 2014 16:55:58 +0000
Received: from BN1AFFO11FD021.protection.gbl (2a01:111:f400:7c10::118) by
 BLUPR08CA0072.outlook.office365.com (2a01:111:e400:88d::52) with Microsoft
 SMTP Server (TLS) id 15.0.1010.18 via Frontend Transport; Wed, 20 Aug 2014
 16:55:56 +0000
Received: from mail-vc0-f171.google.com (209.85.220.171) by
 BN1AFFO11FD021.mail.protection.outlook.com (10.58.52.81) with Microsoft SMTP
 Server (TLS) id 15.0.1010.11 via Frontend Transport; Wed, 20 Aug 2014
 16:55:56 +0000
Received: by mail-vc0-f171.google.com with SMTP id hq11so9516889vcb.30
        for <[email protected]>; Wed, 20 Aug 2014 09:55:55 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=20120113;
        h=mime-version:date:message-id:subject:from:to:content-type;
        bh=UIg592euC1okrJydwvvU1ssSy4p+p3l+Nh+vpxrcn/Y=;
        b=yhVCdHhs616U6+U4K7UqoQwm+eUrFgIJMKqmEUzREUgdgcgFtoM9+5MABnFeEjW7Cz
         RT7vVTlH+v7nH/iW+nntxCRi4I3cqLUcAY8AgM5kGVoGBURCqo66dVbxWghB0HMDiZ7D
         1AMDv1gez/PG8pmOpSVtkg1xmp0a/19vlPcqJ5ZRBlU/HdAuEYRp9M8ZBZLXgYF9RfDg
         PphDqDLqDZ+Y7yNVIbAoC3gHA9kqfqAgWp3HOqRWb5TcRWI7sb9pj5ifYPQBVDJ6ozAS
         jGfhzvxWHnbBPzVKqcCmkgrUVcSX8cUCrZqBjSk6c616nHSjVy6fRHnPdyIJ0Nzd6cnk
         FR5Q==
MIME-Version: 1.0
X-Received: by 10.52.136.196 with SMTP id qc4mr15358922vdb.22.1408553755439;
 Wed, 20 Aug 2014 09:55:55 -0700 (PDT)
Received: by 10.52.178.168 with HTTP; Wed, 20 Aug 2014 09:55:55 -0700 (PDT)
Date: Wed, 20 Aug 2014 22:25:55 +0530
Message-ID: <CA+GyOUV7n1V35=[e-mail]>
Subject:
From: sai siva kumar <[email protected]>
To: <[email protected]>
Content-Type: multipart/alternative; boundary="bcaec51b12bd3d78fb0501127a3a"
Return-Path: [email protected]
X-EOPAttributedMessage: 0
X-Forefront-Antispam-Report: CIP:209.85.220.171;CTRY:US;IPV:NLI;EFV:NLI;
X-Microsoft-Antispam: BCL:0;PCL:0;RULEID:;UriScan:;
Final-Recipient: rfc822;[email protected]
Action: failed
Status: 5.1.1
Diagnostic-Code: smtp;550 5.1.1 RESOLVER.ADR.RecipNotFound; not found
Thanks

Answer 1

Hi,
Have you tried deleting the bad entry in your Outlook or Outlook Web App recipient AutoComplete cache as the error message suggested? If not, please have a try on it.
In addition, this issue may also occur if the on-premises mail-enabled user who represents the moved mailbox isn't stamped correctly with the target address. The Exchange server generates an NDR message because the on-premises Active Directory Domain Services
(AD DS) can't locate the user in order to route the mail correctly. To resolve it, please refer to this KB article:
http://support.microsoft.com/kb/2685437
Also have a look at the following article regarding 5.1.1 error:
http://technet.microsoft.com/en-us/library/dn479208(v=exchg.150).aspx
Since this forum is for questions and feedback related to Office Client side issue, you can also post a question in Exchange Online forum for further assistance:
http://social.technet.microsoft.com/Forums/msonline/en-US/home?forum=onlineservicesexchange
Thank you for your understanding.
Best Regards,
Steve Fan
TechNet Community Support
It's recommended to download and install
Configuration Analyzer Tool (OffCAT), which is developed by Microsoft Support teams. Once the tool is installed, you can run it at any time to scan for hundreds of known issues in Office
programs.