Why is apple email automatically downloading attachments?

I opened an email and the attachment automatically said “downloading”. Is it really downloading? If so, this seems like a security issue; it’s usually clear which emails not to open because they are obviously junk/phishing, but not always. The attachment isn’t in my downloads folder which is hopefully a good thing, but not sure if it is just hiding somewhere else. If it is truly downloading, is there a way to stop this happening automatically? And do I need to take my phone somewhere to have this file removed? Thank you