The ‘ErrorSendAsDenied’ issue often occurs when setting up your website to send emails using Microsoft’s API.
Microsoft usually requires users to authorize their mailbox account to send emails on behalf of their website.
If the email address you authorized during the setup process differs from the one you added to your SMTP plugin, you’ll likely experience this error.
Resolving the Error – Solution
To fix this error, you’ll need to update the email address you set as the From Email to match the one you authorized during the setup process. Be sure to save your changes after updating the email address.
If you’d like to send emails through a different Microsoft account, you’ll need to set up email aliases. See Microsoft’s documentation on sending as or on behalf of another user for more details.
Once you set up email aliases, you’ll be able to use any user’s email address that you’ve configured in your connected Microsoft account.