Sender Permitted From (SPF) is a means for mail servers to verify email was sent from another mail server that is permitted to send mail for the sender's domain. The list of servers is provided in a DNS entry for the domain. All of our hosting packages come with a default SPF record.
We currently recommend you use an SPF record such as:
v=spf1 a/30 a:linnet.elirion.neta:kestrel.elirion.net ip4:38.117.1.0/24 mx -all
This says that legitimate mail could come from the three elirion.net servers listed, or from our data center's mail servers, or from the domain's incoming mail servers, or from the domain's web site. (There is some duplication in this record, but it should work if we migrate your site to a different server.)
You may wish to modify your SPF record. For example, if your ISP is Cox and you send email via Cox's mail servers using your domain name, you should add an entry such as:
include:cox.net
to tell receiving mail servers to include Cox's SPF record when deciding whether email is legitimate.