If the Quickmail "Compose new email" screen is zoomed or is used on a small screen, some of the text areas become covered by course blocks.

To replicate:

1. Create a course and add the Quickmail block
2. Click "Compose new email"
2. Zoom the page to at least 120%. Note blocks are now covering part of the text entry areas on the page.
3. Docking the blocks has no effect; the affected areas now extend off the page.

This is visible in both Clean and More themes.