I'm not sure how to change the default line spacing. But here's a workaround that might save a bit of time and effort:



1. Reformat some text the way you want it to appear.


2. Select at least one paragraph of the reformatted text.



3. Press Ctrl + Shift + C to copy the formatting.



To apply the formatting to another paragraph, move the cursor anywhere within a paragraph. No need to select. Then press Ctrl + Shift + V to paste the formatting. This should change the formatting of the current paragraph, even if nothing is selected.



The "clipboard" containing formatting information should persist as long as Outlook is open.