The line-height property defines the amount of space above and below elements, such as lines of text.
To edit the line-height property, click on the Source button to edit the HTML source code for the message. Find a paragraph tag like this in the message body:
Add the line height property to the text. This property must go inside a style="" section and can be assigned in terms of pixels (px), points (pt), or percentages (%):
You may also want to edit the spacing between paragraphs of text. Do this by adding a style with margin or padding to the paragraph tags: