How To: Set SPF records In Google Apps For Your Domain
SPF (sender Policy Framework) records allow a domain owner to specify which hosts are permitted to use their domain name when sending mail. SMTP is implemented in a manner which allows the sender of an email to claim to be someone else. Spammers and conmen take advantage of this design flaw to send emails with forged From: addresses. The Sender Policy Framework allows a domain owner to use a special format of DNS TXT records to specify which machines/hosts are authorized to transmit email for their domain, making it difficult (but not impossible) to forge From: addresses.
If you are using Google Apps For You Domain and wish to use SPF, you can publish SPF records for your domain. Having these records in place will ensure that messages sent from users in your domain are not rejected by the recipient's domain as well.
To set the domain's SPF record, access the domain's DNS settings. On the DNS resource, publish the following TXT record:
v=spf1 include:aspmx.googlemail.com ~all
ProTip: Publishing an SPF record that lacks include:aspmx.googlemail.com or specifying -all instead of ~all may result in your mail not being delivered.
