E-mail spoofing is the forgery of an e-mail so that the message appears to have originated from someone other than the actual source. Distributors of spam often use spoofing in an attempt to get
recipients to open their solicitations.
Your email address can also be used to trick your customers and suppliers into responding. This is serious as it can damage the reputation of your business.
There is no single solution, but we do have some techniques available to increase the resilience of your email domain name when it comes to spoofing attacks.
This is a DNS record published on the Internet for your company domain name.
The purpose of an SPF record is to prevent spammers from sending messages with forged “From” addresses at your domain.
More info: https://support.google.com/a/answer/33786?hl=en
This is another DNS record published on the Internet for your company domain name.
DomainKeys Identified Mail (DKIM) builds on SPF as another method designed to detect email spoofing. It uses cryptographic authentication to check that incoming mail is genuine.
More info: https://support.google.com/a/answer/174124?hl=en