A program is trying to send an e-mail message on your behalf warning in Outlook

 If you are using a Remote Desktop host and Outlook, you may come across an issue with 3rd party applications trying to send email.

Outlook will give you an warning saying that "A program is trying to send an e-mail message on your behalf"

The quick fix is to add a reg key (DWARD) setting the ObjectModelGuard to 2 as outlined in the following

https://docs.microsoft.com/en-us/outlook/troubleshoot/security/a-program-is-trying-to-send-an-email-message-on-your-behalf

The location changes based on if you have Office MSI, click to run, and 32 bit or 64 bit installed but its also in the following key

Office\<x.0>\Outlook\Security

x being the version of Outlook installed.

If this does not work you can also try the following keys in the same location

"promptsimplemapisend"=dword:00000002
"promptsimplemapinameresolve"=dword:00000002
"promptsimplemapiopenmessage"=dword:00000002
"promptoomsend"=dword:00000002
"promptoommeetingtaskrequestresponse"=dword:00000002
"promptoomaddressinformationaccess"=dword:00000002
"promptoomsaveas"=dword:00000002
"promptoomformulaaccess"=dword:00000002
"promptoomaddressbookaccess"=dword:00000002
"adminsecuritymode"=dword:00000003

But this was the older way to do it and ObjectModelGuard should be the go to at first.