This is an issue that comes across very seldom, but I do run into it every now and then. Microsoft Outlook, by default, allows a maximum of 10 Exchange Accounts per Outlook Profile. Here is the solution that I use to increase the maximum number of Exchange Accounts per profile.
The solution below applies to Outlook 2010 to the latest version.
Search for REGEDIT in Windows and click “Run as Administrator“
Then browse to HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\Exchange.
You might not have the key “Exchange” so you will have to create it.
Then in the Exchange key, right-click and create a new DWORD and call it MaxNumExchange.
Edit the new DWORD, select Decimal, and set the number of Exchange Accounts you want to be able to add in Outlook.
Now you need to repeat the above but you need to browse to HKEY_CURRENT_USER\SOFTWARE\Microsoft\Exchange.
Create the key “Exchange” if it’s not there and create a DWORD also calling it MaxNumExchange.
Edit the new DWORD, select Decimal, and set the number of Exchange Accounts you want to be able to add in Outlook.
In my example below I increased the maximum number of Exchange Accounts per profile to 50.
