Do not open email attachments from an unknown, suspicious, or untrustworthy source. If you're not familiar with the sender, do not open, download, or execute any files or email attachments. Do not open an email attachment unless you know what it is, even if it appears to come from a friend or someone you know.

Is opening an unknown email Bad?

Most users get viruses from opening and running unknown email attachments. Never open anything that is attached to an email message unless you know the contents of the file. ... If you receive a message with an attachment and you do not recognize the sender, you should delete the message.

Why is it not advisable to open emails from unknown sources?

Don't open them. The messages often are loaded with language designed to encourage the recipient to open the attachments, which could be loaded with malware that automatically downloads onto the computer. The basic rule of thumb: If you don't know the sender, don't open the attachment.