Where does "send to" "Mail recipient" in Windows 10 file menu temporarily save files?
Solution 1:
AppData\Local\Temp under your user folder.
From here:
Enter %temp% in the Windows search bar. This will pull up the AppData\Local\Temp folder.
The resized photos are in this folder. (Search or sort by to find .jpg, etc.).
However, note: the files will all disappear from the temp folder if you close out of the mail warning that pops up after selecting to send to mail recipient:
or
So don't click OK on the pop-up until after you've copied the temp files to a new folder.