“If you’re running low on disk space on your Mac, especially SSD space, every extra bit can count,” Allyson Kazmucha writes for iMore. “One of the places you can often scrape out a few extra megabytes or even gigabytes is Mail Downloads.”
“Any attachments you open in Mail or Quick Look gets saved right to that folder,” Kazmucha writes. “Chances are you don’t need them, especially the old ones, and trashing them will free up some valuable space.”
“If you send and receive a lot of email, it’s very easy for the Mail Downloads folder to get extremely large,” Kazmucha writes. “Checking it every few weeks or months, whatever is appropriate for your use case is a good idea.”
More info in the full article here.
Chances are you don’t need them……this tells us immediately that this person does not get it: It is a temp folder. You DON’T need it, period! The attachment will still be with the mail message…..opening it again will just put it back there…..where you still do not need it, for it is a temp folder, not the download folder.