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

When sending and email from an application (i.e., Sage) via Outlook, you may see the below pictured prompt.

If clicking 'Allow' doesn't resolve the issue, please follow the below steps:

In Outlook, navigate to File - Options - Trust Center - Trust Center Settings -Programmatic Access

Change selection to 'Never Notify.'

Click Ok.

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