The open standard that checks to determine if your email address is valid is called SPF ( Sender Policy Framework ). The SPF record is one of the DNS records which stores information and regulates your domain names’ functions. The main use of SPF is to stop email SPAM, which mostly originates from forged addresses. SPF records are the ideal way to prove that an email did indeed come from your domain’s mail servers.
When an email goes out without a defined SPF it could have come from pretty much anywhere. That’s precisely the reason why most email systems won’t accept messages if they don’t come with an SPF record. They’ll either reject them or treat them as SPAM. Gmail, Hotmail, Yahoo, AOL and others require your SPF record and their networks won’t let you send email without one. So, it’s important to be sure that your email and web hosting services will let you set SPF records.
When your message goes to a mail server, it checks your DNS records for the SPF. If it finds one then it looks to see if the email came from the same server mentioned in the record. You can put an SPF in the TXT record to show which servers are allowed to send email messages from your domain. For example, when you send emails from [email protected] the SPF records should include mysuperdomain.com, which validates the domain.
You could also add more of your domains but be aware that the most SPF record checks that can be done is set at 10 DNS lookups. The functions used in SPF that require DNS lookups are “include”, “a”, “mx”, “ptr”, and “exists”, part of this list is the “redirect” modifier also.