Uploading an image

WordPress stores uploads in one folder, default is called wp-content. You can change the name or move it elsewhere. You can also use plugins to manage the media folders differently than WordPress does by default. But there is nothing stopping you from doing it the way you were doing before. If you don’t want to use the image in WordPress, there’s no need to use WordPress to upload it.

Thanks Joy, so if I upload the image to https://www.test.com/wp-content via FTP would I then have the path in my HTML emails to it, as https://www.test.com/wp-content/image.jpg ?

Yes