You can resize SVGs by dragging a corner instead of using the scale command. Scaling an SVG will cause rending problems.
Here's an example, where the image is dragged directly onto the scene: mail.zip (15.4 KB)
Your SVG file shouldn't have a 'viewbox', which will limit its ability to be resized. You can use this tool to remove it: https://jakearchibald.github.io/svgomg/