In an attempt to minimize spam and improve the deliverability of legitimate email we are now spam filtering outbound email send via This service is know as Outbound Email Outbreak Protection


For individuals trying to send outbound email via the smtp server using a from address that includes the name of a consumer webmail service or residential ISP you may receive sending errors related to SPF records. In this case you will need to use the reliable smtp server that your ISP or webmail provider has specified in your account with them. 

DuoCircle will no longer relay these messages reliably because you as an end user are using the the DuoCircle outbound servers in a way that is not compliant with Internet standards. 

This means if you are trying to send as,,,, or other consumer services and you are getting errors you will need to use the settings and outbound mail servers from these ISP's.

Due to SPF records that these ISP's publish (not DuoCircle's blocking) they do not authorize any SMTP servers other than their own to send email on their behalf. This is not a Duocircle specific issue, this is an internet wide issue as a way to minimize spam. 


If you are a business with your own domain name you should not have any issues sending via the  servers, in fact things should flow faster and your deliverability should be better since we have made these changes because there is less spam on our networks. 

You should update or create an SPF record for your domain based on the information in this KB article -

This will notify receiving mail servers that you authorize and permit to relay mail on your behalf. 


Link to a comprehensive set of knowledge base articles to help you resolve any errors that you are receiving while trying to send email via our service Outbound Email Outbreak Protection