How to check files received by emails whether they have virus

  Most of the computer viruses are spread via email attachments. It is better to install a virus scanner on your computer.
Best thing
Do not Double click on the attachment.
just save it on a temporary folder
open a web browser and visit the website

https://www.virustotal.com/

Select Choose File
Scan

it will Scan from known virus scanners.
when you see the results, you know the file. you can make sure about the file that doesn't contain a virus.