If you utilize Smarsh's smarshEncrypt service with your Redtail-hosted email, Redtail and Smarsh recommend that you create a Sender Policy Framework record, commonly referred to as an SPF string/record for your domain. An SPF record is a type of record attached to your domain that identifies which mail servers are permitted to send email on behalf of your domain. The creation of an SPF String would be made at the domain host level. Some common domain hosts are GoDaddy, Network Solutions, 1and1, and Emerald.
The purpose of an SPF record is to discourage spammers from attempting to send messages with forged "From" addresses at your domain. This process is generally referred to as Spoofing. Recipient mail servers can refer to the SPF record to determine whether a message purporting to be from your domain is coming from an authorized mail server for your email address.
It is recommended that you add Smarsh's SPF string/record value as all outgoing mail is sent through Smarsh's outbound relay when utilizing their encryption service with your Redtail hosted email service.
Smarsh's SPF String Value: v=spf1 include:spf.smarsh.com -all
For instructions on adding an SPF String within GoDaddy.com, click here.