I have a spring boot application with an angular frontend running on AWS. When a new user signs up, he receives a mail with a url containing a confirmation code. When the user clicks on that url, the application marks the mail address of the user as confirmed. This works nicely when I'm running the application on localhost.
When I run the application on AWS, around 10 seconds (!) after the user has signed up, the url in the mail with the confirmation code is automatically called, WITHOUT anyone clicked on that url in the received mail. Any ideas how this can happen? Maybe some kind of mail scanner sitting anywhere and checking links inside sent mails? This sounds very strange to me, but I can't imagine any other reasons?