The paragraph spacing is controlled by the styles and formatting setup that you have.

The simpliest way is to draft your emails in plain text. No paragraph spacing is involved.

Alternatively, if you prefer to send HTML emails, go to the "Format text" tab, right click on the normal style, select modify.

Then click the the bottom left "format" button, select "paragraph...".

Under "spacing", change the values to 0 for both before and after.

Jay