Anonymity is virtually impossible for anyone to trace back an email sent anonymously. Spoofing an email with a false sender address is relatively simple since the Simple Mail Transfer Protocol (SMTP) does not check the information in the Reply toFrom, Sender fields. To pull off a completely untraceable spoofed email the sender will have to use a VPN to mask their IP address or use a compromised system to send the emails from. Compromised servers are popular with people running malicious email campaigns.”]
Source: https://blog.malwarebytes.com/101/how-tos/2021/07/how-to-send-an-anonymous-email/