Download attachment in Mail application is super slow

Whenever I download attachment from an email in Mail application, it super slow. It's 10 times slower than when I download the same attachment from Safari. So it means not because of the internet speed.

I don't know you guys have the same problem like me.

And another quesion, can we configure Mail app to automatically download attachment. Now everytime I receive an email, I have to open email and click on attachment to download it. It waste time to sit there and wait.