Deliverability update: SFR on his way to a stringent filtering process

Through the last few days we have noticed — via our customer’s deliverability monitoring infrastructure — SFR’s enhancement of its filtering policies. For instance, we notice a bigger number of the ‘550.5.7.1 Message Content rejected’ messages after running the DATA command during SMPT dialogs.

As far we can see, this enhancement is based on the employment of ratios between qualitative and non-qualitative senders per IP address. Previously in our blog, we lured attention to the fact that SFR employed bounce rates and spam-report rates to lever when to block an IP address or not : this sheds light on an ongoing evolution of its filtering process. Within this framework, spam reports become an important mechanism when deciding if an email should fall into the spam folder or into the inbox. Based on our observations, the rate of acceptable reports remains the same as that of the industry’s standard.

It is important to remind that Signal Spam’s Feedback loop holds the only access to the SFR’s IP-generated reports figures.

SFR moves forward to follow the same path others in the field do: deliverability-threatening email flow must remain isolated from the rest of the strategical or more relevant emails. In practical terms, this means setting apart IP addresses and domain names operated by these flows.

It has been also noticed that the before-said ratios have not been utterly set by SFR, and that SFR is more likely to be currently setting up its employed thresholds. We will keep you informed as we get deeper in the subject.

Reminder: Below the list of the involved domain names :,,,,,,,,,,

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