How should I process FBL reports to suppress complainers?

If you're sending at any real volume, FBL reports will land in your pipeline whether you're ready for them or not. The question isn't whether to process them. It's how fast and how cleanly you do it.

What an FBL report actually looks like

FBL reports arrive in ARF (Abuse Reporting Format), which is essentially a multipart email message. It contains a human-readable summary, the original complaint notification, and a copy of the email that triggered the complaint. The piece you care about most is the Original-Rcpt-To or Feedback-Type headers inside the ARF payload. Those fields carry the complaining address. Once you extract that address, you suppress it. That's the whole job.

Does your ESP handle this automatically?

For most senders, yes. The big marketing platforms take care of FBL processing without you touching a line of code. Mailchimp, Klaviyo, Brevo, ActiveCampaign, and MailerLite all handle spam complaints natively. When someone hits the spam button, those platforms suppress the address before your next send. You don't need to configure anything.

Transactional and API-focused senders are a different story. If you're using Twilio SendGrid, Mailgun, or Amazon SES, you'll want to check your dashboard or webhook settings. SendGrid and Mailgun both offer event webhooks that fire on complaint events. You can point those webhooks at your own system to trigger automatic suppression without writing a custom parser. Amazon SES routes complaint notifications through SNS (Simple Notification Service), which you subscribe to and handle in your backend.

What if you manage your own infrastructure?

Then yes, you'll need a bit of code. You configure a dedicated mailbox to receive FBL reports (something like fbl@yourdomain.com), then write a listener that parses incoming ARF messages and writes suppressed addresses to your database. Parsing libraries exist in Python, PHP, Ruby, and Node. It's not a complex build, but it does need to be reliable and always on. A queued job that runs once a day is not good enough here.

How fast should suppression happen?

Immediately. Within minutes of the report arriving, not batched overnight. The whole point of an FBL is real-time signal. If you're sitting on complaints and sending to those addresses the next morning, you're burning your sender reputation with every send. Automate the suppression pipeline so it runs on receipt, not on a schedule.

How long does someone stay suppressed?

Permanently, in almost every case. There's no standard re-engagement window for someone who explicitly flagged your email as spam. They've told their mailbox provider they don't want your mail. Emailing them again (even months later) risks another complaint, and complaints impact inboxing faster than most people expect. Keep them on your global suppression list and don't second-guess it.

What to log alongside the suppression

At minimum, record the timestamp, the campaign or message ID that triggered the complaint, and the mailbox provider that sent the FBL. Over time, this data tells you which sends are generating the most friction, which is often more useful than the suppression itself. If one campaign type consistently drives complaints, that's a content or targeting problem worth fixing upstream.

Not sure if your current setup is actually suppressing complainers correctly? Our SOS hotline is free. We'll take a look at your configuration and tell you honestly what's missing.