Lync Error Message “This message may not have been sent to because the server timed out”

Microsoft Lync has great potential as a chat and collaboration tool, especially for busy and large offices. The problem is – I find this tool to be really buggy. It will take some time until Microsoft comes up with a decent – stable – version.

The other day, one of my colleagues had a problem with Lync. Sometimes when she tries to send a chat message on Lync, she gets the following error on the chat screen:

“This message may not have been sent to because the server timed out”

Lync - This message may not have been sent to because the server timed out - error message
Lync – This message may not have been sent to because the server timed out – error message

Usually this message shows up when the server doesn’t succeed in sending the message, due to server error or when the other user has gone offline.

The Solution

So after uninstalling Office 365 64bit and installing Office 365 32bit which didn’t solve the problem, I tried to run The Office 365 Repair feature, with no success either.

I then called Microsoft and they recommended to clear Lync’s cache.

This is how it goes:

1. Go to “C:\Users\Username\Appdata\Local\Microsoft\Office\15.0\Lync\” and delete the specific user’s sip (Session Initiation Protocol) folder.

2. Go to “C:\Users\Username\Appdata\Local\Microsoft\Office\15.0\Lync\ Tracing\Delete All files. DO NOT DELETE ANY FOLDER.

3. Open the registry editor (Start + R -> type regedit -> Enter), go to “HKEY_CURRENT_USER\Software\Microsoft\office\15.0\Lync” and delete the specific user’s expandable sip profile folder (the one that contains the user’s email address to sign in to Lync):

So far so good. Will keep you posted if it doesn’t solve the issue.