Describe two measures you can use to evaluate whether an attachment in a message is reliable to open.

If a attachment is not reliable to open, terrible effects can happen, peradventure it may have a virus or even malware that can destroy a computers software. 

To avoid this and stay on the safe side, try the following:-

- Open it in protected view 
- Do not save the attachment on your computer 
- Look at the author and read the message carefully to make sure it is not biased. 
- Open it on a flash-drive 

To have safety measures when opening a file and you dont know if it is reliable or not you should:

Scan the file with an antivirus. ( I prefer Avast )
Open the file in protected view.
Only open the file if you know who sent you the file or where you got it from