Ubuntu Security :: How To View Email Attachment Without Risk

I have received an email with a .csv attachment from a bank, and need to know how to view the attachment without risk. Using View>Message Source I see a large solid block of random upper and lower case characters, whereas I would expect to see some readable text mixed in. The email subject and the attachment name both contain data specific to me, but the text of the email consists largely of disclaimers with no mention of my name or any clue as to the nature of the attachment. I am using Thunderbird as my email client.