Hide emails on send

I have a third party application that is using eMClient to simply send emails using SMTP. It also attaches a file to each message it sends. This works fine. However, even with eMClient minimised it always displays the email to be sent for a few seconds on the screen before it then disappears and gets sent. Is there a way to stop this behaviour so the email isn’t seen by the User on the screen before sending? I’ve turned off spell checking etc, but I suspect that’s not the problem anyway?

Many thanks,