My teacher told me that my e-mails are sometimes regarded as spam mails and she couldn't download attached files. But, after a while she managed to download them.
One of the strange points is that time allows her to download them. Once we are rejected to access attached files, we wouldn't download them semipermanently.
Another of the strange points is that the domain of my e-mail address is owened by my university. I've never heard that an universities' web mail was treated as a spam mail.
I guess she is poor at operating her computer.
