The character  present in <spacer>'s source is being rendered as a visible space on Apple Mail's preview but not on the actual message (tested on 9 and 10). Switching it to a regular seems to sort the issue. Any reason not to use instead?
The character
 
present in<spacer>
's source is being rendered as a visible space on Apple Mail's preview but not on the actual message (tested on 9 and 10). Switching it to a regular
seems to sort the issue. Any reason not to use
instead?The layout source code (full message dist code here):