Lync 2013 generates repeated messages stating Either there is no default mail client or the current mail client cannot fulfill the messaging request. Please run Microsoft Outlook and set it as the default mail client.. Events that seem to generate messages is disconnecting and re-connecting to a network but it also happens randomly and the messages will stack up during a working day. Everything seem to work OK but it is an annoyance.  The computer is upgraded (uninstalled first) from Office 2013 ProPlus to Office 365 ProPlus. Outlook (Desktop) is default mail client. 64-bit Windows 8.1 Enterprise, 64-bit Office (both before upgrade and after).  

(Links removed to remediations I've tried)

Made no difference what so ever and the messages continue. What's next? 

I posted the above to the Office 2013 forum (unfortunately I'm not allowed yet to post a link to that posting) but due to the fact that the computer affected by this is a networked domain computer I've been redirected to this group instead.  I was asked some additional questions ing the other forum regarding the problem: 

Are you able to send mails from other applications like Word or Excel? NO

Is the PC connected to any Domain/Server? YES

Is this an issue with one PC only. NO - affects all computers that once had Office 2013 Pro Plus installed and now has Office 365 Pro Plus (Originally I posted this question in the Office 365 community but was directed to first the Office 2013 forum and now this forum)

Right click on any file and Click on Send to-> Mail Recipient and check if you are able to send mails using Outlook. NO

Also check if the Lync add-in is enabled in Outlook.

Start Outlook

Click the File tab.

Go to Options.

Click Add-ins.

Check if the Lync add-in is enabled. YES

My last posting in the other forum contained the following additional information regarding our problem: 

As far as we can see installing 32-bit Office 365 Pro Plus using click to run makes no difference. 

We do not send any mails from Lync, Lync is however the process that generates the message most frequently (as Lync seem to react upon network events). Other processes that have Outlook plugins may also be the parent of the message popup (third party applications). 

Yes the Lync add-in is enabled. Lync functionality in/from Outlook seem unaffected. 

It is not possible to send emails from other applications (explorer, word, excel etc.) ie. right clicking and send to generates the messages and a follow up error message concerning lack of MAPI enabled e-mail. 

Hi,

It's not a stand alone version of Outlook, correct?

This issue may occur if the Outlook registry key is corrupted. When other programs try to use the Outlook Simple MAPI interface, they cannot retrieve the required information from the registry.

We may try testing the following steps on a problematic computer to see the result:

1. Press Windows key + R to open the Run command, type regedit in the blank box and press Enter.

2. In Registry Editor, locate the following subkey:

HKEY_LOCAL_MACHINE\Software\Clients\Mail\Microsoft Outlook

3. Right-click the subkey, and then select DELETE. Click Yes in the confirm dialog.

4. Quit Registry Editor.

5. Now, go to Control Panel, click Programs and Features, right-click Office 365 ProPlus and then click the Change.

6. Next, click Quick Repair or Online Repair, and then click Repair.

7. Follow the instructions on the screen to complete the repair.

8. Restart Outlook and test the issue again.

Please let me know the result.

Regards,

Steve Fan

Forum Support