Send function SPAM despite being turned off

It seems that bots are somehow accessing the send function on SFL and sending out links to files I’ve uploaded. I am seeing numerous “delivery failed” emails because some of the recipient mailboxes are full. I’m not sure how this is happening. I don’t have the send link enabled. The emails are in Spanish, have a random string of letters in the subject, link to files I’ve uploaded with SFL, and have a footer that says “Sent from the file list at [ADDRESS]”

Any idea how to make this stop happening?