no default mail client

Have you been getting these errors?


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.

Well! I get it a lot as well. Let me tell you why it happens and how to fix it!

Different bitness

If the program you are trying to email from is a different bitness from the Outlook you have installed; you will get this error. For example:

  1. If you have 64bit Outlook installed and try to email from a 32bit application.
  2. If you have 32bit Outlook installed and try to email from a 64bit application.

In the above scenarios you will see the default mail client error. There are some work arounds though!


  1. Uninstall your current version and install the other version.
    1. If you have 64bit Office, uninstall it and install 32bit Office
    2. If you have 32bit Office, uninstall it and install 64bit Office
  2. If you have 64bit Outlook installed I believe it is possible to have 32bit applications email correctly. Follow the steps here on this webpage.

I have not tried the instructions but from a cursory glance they look reasonable.

Unfortunately I have not found a way of emailing from 64bit applications with 32bit Outlook installed. Except there is a hack to do if for .NET applications!

.NET Applications

When .NET applications are built in Visual Studio, most of the time they will be built with platform of Any CPU. .NET applications have the advantage of running across multiple CPU types. If you run a .NET application on a 32bit computer it will be 32bit, run it on 64bit and it will be 64bit. Sounds Amazing!

Well, it’s not that amazing because we have 32bit Office installed on a 64bit computer. These .NET applications are deciding to run as 64bit applications and because of this they are throwing this error around like monkeys flinging poop. There is a solution!

Grab corflags.exe off MSDN, and then run it on the .NET application you are having trouble with:

corflags.exe dotnetexecutable /32BIT+ /Force

This tells the application to be 32bit in 64bit environments. I have tried this on several applications and it’s fixed the issues I was having.

Email Client registry settings are incorrect

Just so you know, I have very VERY rarely actually found that the client registry settings are incorrect. But hell, the steps to fix the registry settings can be found in Microsoft KB813745.

Hopefully the above helps you out!