Cloud Server for Email
cloudserverforemail.com · infrastructure@cloudserverforemail.com · +372 602 3545
EU-Based Infrastructure
Operating Since 2015
Operating Since 2015
FBL (Feedback Loop) Processing Guide
Complaint Feedback Setup and Automated Processing
Version 2026-04 · Cloud Server for Email
Available FBL Programs
| ISP | Program | Registration URL | Format |
|---|---|---|---|
| Yahoo/AOL | Yahoo Postmaster FBL | senders.yahoo.com | ARF (full original message) |
| Microsoft | JMRP | sendersupport.olc.protection.outlook.com/jmrp | ARF (full original message) |
| Comcast | Comcast FBL | postmaster.comcast.net | ARF |
| Gmail | No FBL (use Postmaster Tools) | postmaster.google.com | Aggregate only |
ARF Format: Extracting Complaint Data
# ARF complaints arrive as multi-part MIME emails
# Structure:
# Part 1: Human-readable summary
# Part 2: machine-readable (Content-Type: message/feedback-report)
# - Feedback-Type: abuse
# - User-Agent: ISP-name
# - Original-Mail-From: return-path of original
# - Arrival-Date: when ISP received it
# Part 3: Original message (headers only or full)
# Extract recipient from original message:
# From the Original-Rcpt-To header in the feedback-report section
# OR from the List-Unsubscribe header in the original message
# OR from the X-Campaign-ID or custom tracking headers you added
Processing FBL Complaints
- Set up dedicated mailbox for FBL complaints (fbl@yourdomain.com)
- Register mailbox with each FBL program
- Parse incoming ARF emails: extract Original-Rcpt-To or List-Unsubscribe
- Add extracted address to global suppression list immediately
- Log complaint: timestamp, ISP, source campaign ID
- Calculate daily complaint rate: (complaints / messages sent to ISP) × 1000
- Alert threshold: >1 complaint per 1,000 messages to Yahoo → investigate immediately
PowerMTA Pipe for FBL Processing
# Inject FBL complaints back through PowerMTA pipe for processing
<domain fbl-processing.internal>
type pipe
command "/usr/local/bin/process-fbl.sh"
</domain>
# process-fbl.sh reads stdin (ARF message), extracts recipient,
# calls suppression API to add to suppression list
MailWizz FBL Configuration
- Backend → Servers → Feedback Loop Servers → Add
- Enter IMAP credentials for the FBL complaint mailbox
- Set processing frequency: every 10 minutes (via cron)
- MailWizz automatically parses ARF and adds to suppression list
Complaint processing latency matters. FBL complaints processed immediately (under 10 minutes) prevent the same address from receiving the next campaign send. Batched daily processing can mean the same complainant receives another email before being suppressed.