<div>
Morning,<br />
<br />
Have you made any changes to these accounts recently? Any sort of migration or anything?<br />
<br />
I'd try 2 things, Firstly clear the entry from the NK2 file (basically start typing and hit the cross next to the name and try again.<br />
<br />
Manually type the entire address from an external mail account I.E google.<br />
<br />
See if either of those work, if it doesn't let me know. <br />
<br />
Regards<br />
Alex
</div>


Morning,

Have you made any changes to these accounts recently? Any sort of migration or anything?

I'd try 2 things, Firstly clear the entry from the NK2 file (basically start typing and hit the cross next to the name and try again.

Manually type the entire address from an external mail account I.E google.

See if either of those work, if it doesn't let me know.

Regards
Alex

<div>
are the addressees with the problems in the offline address book in Outlook?<br />
<br />
also are you running in hybrid at all? or solely 2013
</div>


are the addressees with the problems in the offline address book in Outlook?

also are you running in hybrid at all? or solely 2013

<div>
<div class="content wysiwyg-content">
Hi, <br />
<br />
I have an odd issue with 3 users, when anyone in my company tries to email these 3 from Outlook the mailtip ‘We won't be able to deliver this message, because the email address is no longer valid’ appears in Outlook (2013)<br />
When emailing from OWA the message does not appear.<br />
<br />
I have checked the AD attributes these look ok, <br />
We are using exchange 2013.<br />
Any suggestions on what to check?<br />
<br />
Thanks
</div>
</div>


Hi, 

I have an odd issue with 3 users, when anyone in my company tries to email these 3 from Outlook the mailtip ‘We won't be able to deliver this message, because the email address is no longer valid’ appears in Outlook (2013)
When emailing from OWA the message does not appear.

I have checked the AD attributes these look ok, 
We are using exchange 2013.
Any suggestions on what to check?

Thanks

We won't be able to deliver this message, because the email address is no longer valid

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

Exchange

Microsoft Outlook is a personal information manager from Microsoft, available as a part of the Microsoft Office suite. Although often used mainly as an email application, it also includes a calendar, task manager, contact manager, note-taker, journal, and web browser.

Outlook

Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.