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Cannot send out client event notifications

This article was created in response to a support issue logged with K2. The content may include typographical errors and may be revised at any time without notice. This article is not considered official documentation for K2 software and is provided "as is" with no warranties.


Unable to send out client event notifications due to the following error:

The specified string is not in the form required for an e-mail address.


The From Address and e-mail address of the recipient are all valid.

Below is the complete error message on host server logs:
"Error","MessageBus","61007","SendMessageException","MessageBusRuntime","61007 Permanent failure sending message [E-MAIL SUBJECT] : System.FormatException: The specified string is not in the form required for an e-mail address.

Troubleshooting Steps

  1. Decrypt the K2HostServer.exe.config file by following the steps below: 
    • Copy the K2HostServer.exe.config file from [InstallDrive]\K2 blackpeal\Host Server\Bin to C:\Temp
    • Once the file has been copied to C:\Temp, rename it to web.config
    • Open cmd as administratior and change the directory to: C:\Windows\Microsoft.NET\Framework\v2.0.50727
    • Run the following: aspnet_regiis -pdf "connectionStrings" C:\Temp
  2. Open the web.config file on a text editor and look for the following connection strings:

       <add name="HostServer" ... />
       <add name="WorkflowServer" ... />
  3. Ensure that the connectionString value for these keys are pointing to the correct K2 server.
  4. If there's a need to edit the value, copy the contents to the K2HostServer.exe.config
  5. Save the file.
  6. Restart the K2 blackpearl service.

Please make a backup of the K2HostServer.exe.config before making any changes.