Dynamics AX is integration with Microsoft Office Outlook for sending E-Mails, doing synchronization in the CRM Module, etc.
In several occasions you can get confronted with the following or a similar error message:
A very common reason for this error is that the mapi32.dll in the System32 sub folder of your Windows folder is not the one originally installed by your Microsoft Office Outlook version. This often happens when your are installing another application that is using MAPI after you have installed Microsoft Office Outlook.
In order to fix this you can try to repair your Outlook installation which will usually also replace the mapi32.dll, however this might affect the application that has replaced the DLL.
In this scenario you can also place the mapi32.dll shipped with your Microsoft Office Outlook installation in the bin folder of your Dynamics AX Client's folder (e. g. C:\Program Files\Microsoft Dynamics AX\50\Client\Bin).