If you are an Access Hosted Client then please check the following items.
Within Windows:
Ensure that you have 32 bit Outlook installed and not 64 bit Outlook, as Dimensions is a 32 bit program it won't work with 64 bit versions (please contact your own IT team if you require support with this).
Check that Outlook is selected as the default Email under Default apps within the Control Panel.
Within Dimensions:
Click System, User Records.
Select the relevant User and check the E-mail Setup is set to the correct setting (SMTP or MAPI)
Click System, Options, System Control, System Format.
Check the System E-mail Defaults details are correct.
If you are have checked these settings are still seeing the error message then please raise anew caseonline and reference the title of this article and please include details of the user affected.