I never open an e-mail attached file if I do not know whom it is from. Yesterday I received one which the 'Spam File' isolated from booked.com advising me that I had electronically booked a luxury hotel in Instanbul with reference no. dates, details and attached file. I have resisted opening the attached file and checked the website out which appears genuine. I am concerned that my e-mail address has been used falsely. What to do is the question, delete or open up and investigate further? All seems ok with bank account.
Legitimate e-mails from companies nearly always contain some personal details about yourself such as your name, address, last digits of credit card etc. If you get an unsolicited one lacking such details then it's almost certainly a scam or phishing e-mail, or contains a malware-laden attachment and should be deleted immediately. Whatever you do, do not open the attachment.