When attempting to set up emailing through the Lasernet Connector, the following error message may pop up. This affects Report predefined destinations and standard Lasernet Emailing:

Cause
 
D365 FO version 10.0.25

Microsoft has introduced a new HTML editor control and no longer supports the Legacy HTML editor in version 10.0.25.
 
Updates to client feature states with version 10.0.25 - Dynamics 365 Release Plan | Microsoft Docs 

Lasernet Connector Parameters are set to Legacy HTML editor which does cause an error message to pop up when entering the destinations for emailing. This is due to update 10.0.25 of D365 FO. 

Solution

To stop this message from popping up,  follow these steps:

1. Navigate  to Lasernet > Setup > Parameters > Email  -

2. In the Emailing body editor type field, change the value to HTML editor.

If you are using a Lasernet Connector version prior to 6.16 and do not use HTML for email body text, you can also switch to Plain text.