This document sets out some basic info on how to integrate our DNS and Dyn Email services with SPF (Sender Policy Framework). For more info on SPF, vist

DuoCircle Standard SMTP

Customers using only our DuoCircle Standard SMTP service to send mail for their domain may want to add an SPF record for their domain listing our server as permitted to send mail for their domain.    

"v=spf1 ~all"

    This will let you piggy back on the SPF record which we in turn publish for

Problems with too many SPF records?

If you are using the DuoCircle SPF records in conjunction with another provider there is a chance that you will exceed the 10 lookup limit. In this instance please use:


"v=spf1 ~all"


The limitation of this version of the SPF record is that you are restricted to use the mail server and not smtp6-8 in your records. 

 DuoCircle Email Gateway and Backup MX

Customers using our DuoCircle Email Gateway or Backup MX services and who have setup SPF testing on their end, will want to configure their systems to “skip” our servers.

In order to maintain the reliability of the DuoCircle Email service, it may (will) be necessary to add/move machines providing this service from one location to another. Please use the SPF records and not the IP addresses of the servers. 

The only thing we can promise with respect to this service is that all mail will be delivered from IP addresses which have proper reverse and forward DNS within the domain.

Please see the documentation for your MTA and /or SPF implementation for info on how to skip IP addresses when performing SPF tests.

DuoCircle Email Forward

We have no plans to implement SRS (Sender Rewrite Scheme) in DuoCircle Email Forward at this time. As a result, if you are forwarding mail to a domain that has implemented SPF filtering this may prevent you from receiving some mail sent through this service.