Just because an email message looks like it came from your mom, grandma, or boss doesn’t mean that it did. Many viruses can „spoof” the return address, making it look like the message came from someone else. If you can, check with the person who supposedly sent the message to make sure it’s legitimate before opening any attachments.
This includes email messages that appear to be from your ISP or software vendor and claim to include patches or anti-virus software. ISPs and software vendors do not send patches or software in email..