It's only a trojan. Just kidding. Seriously don't open the attachment. More than likely your AV will catch it anyways.
It was just a matter of time before someone came up with the idea to spoof
UPS emails. The list of companies who have been the subject of spoofed emails for phishing schemes (most popular) goes on and on. Unfortunately, there is very little that
UPS (or any other company for that matter) can do. This is where you rely on either a) smart users to not fall victim to the scam or b) up to date antivirus/antispam software to catch the bad stuff before it gets to your inbox.