Hello there,
I already shared with support this issue.
After hours of search, as I can’t reopen that topic, I share here a solution I found (the ones from the initial topic don’t seem to work anymore).
Problem :
When using Gmail Pack formula to send a “non-rich” text, line breaks seem to be doubled :
(Simple) solution :
Replace linebreaks in the text with < br> : [Text].RegexReplace("\n", "<br>") 
Hope that helps