That’s actually a response message in Contact Form 7. If you go to Contact Form 7 Settings you’ll see the field to edit that text.
# Sender’s message was sent successfully
It’s in your plugins code:
email-before-download.php, around line 672.
$cf7->additional_settings .= "\n". "on_sent_ok: \"document.getElementById('wpm_download_$dId').style.display = 'inline'; document.getElementById('wpm_download_$dId').innerHTML='<strong>The link to the file(s) has been emailed to you</strong>.'; \"";
Hello,
Thank you for your post. We will look into adding this as a feature.