Perspective Grids is made by one person, so this is the whole contact department. Everything below reaches Sara Emily directly.
What to send
A mistake in a lesson. Quote the sentence and say what is wrong; it gets fixed and the page’s “updated” date changes.
A bug in a tool. Paste the share link (the Share button puts the exact settings in the URL), say which browser and device, and what you expected to happen.
A grid that does not exist yet. Describe the drawing you are trying to make, not the feature. The box generator and the scale-figure template both started as emails.
Teaching with it. Classroom use is free. If you want a printable set for a course, say which grids and paper size.
Elsewhere
Notes on drawing and tools are on Substack. Who makes the site and how the grids are computed is on the about page.