Received email from someone who didn't send it

That's a strange and potentially concerning situation!

If you've received an email from someone who didn't send it, it's possible that:

Your email account was compromised: Someone may have gained unauthorized access to your email account and sent the email. Check your account's security settings and look for any suspicious activity.
The email was sent by mistake: It's possible that the email was meant for someone else, and the sender accidentally sent it to you instead.
The email was forged: Someone may have created a fake email that appears to be from the original sender, but it's actually a phishing attempt or a spam message.

To investigate further, you can:

Check your email account's sent folder: Look for any emails sent by the supposed sender to see if they actually sent the email.
Contact the supposed sender: Reach out to the person who supposedly sent the email and ask them if they sent it. If they didn't, it may indicate that their email account was compromised.
Report the email to your email provider: If you're using a web-based email service like Gmail, Yahoo, or Outlook, report the email to their abuse department. They may be able to help you identify the source of the email and take action to prevent similar incidents in the future.
Be cautious with links and attachments: If the email contains links or attachments, don't click on them or open them. They may be malicious and could compromise your device or steal your personal information.

Remember to always be vigilant when receiving emails, especially if they seem suspicious or unusual.