"Email spoofing takes advantage of the fact that email, in many ways, is not very different from regular mail.
Each email has three elements: an envelope, a message header, and a message body.
An email spoofer puts whatever they want into each of those fields, not just the body and “To:” fields. This means they can customize the information in the following fields:
Mail from:
Reply to:
From:
Subject:
Date:
To:   "
www.fortinet.com/resources/cyberglossary/email-spoofing

The .gov page
www.gov.uk/report-suspicious-emails-websites-phishing
says
Forward suspicious emails to
report@phishing.gov.uk

Does it have any effect?

Do you have links other pages which have good advice?