Case Study
How Landmark Ventures Recovered From a 0% Inbox Crisis to 95% Placement in a Five-Phase AWS SES Rescue
A 91% cut in bounce rate, zero complaints held for 12+ weeks, and a HEALTHY AWS account, all without pausing the business.
Segment: B2B Executive Outreach | Use Case: AWS SES Email Deliverability Consulting | Industry: B2B Executive Outreach
The challenge
A Deliverability Crisis Threatening Fortune 500 Access
Landmark Ventures is a B2B executive outreach firm serving Fortune 500 clients, where the ability to reach C-suite and senior leadership at target accounts is the business. When they engaged AllCode in March 2026, their AWS SES infrastructure was in full crisis: 0% inbox placement at Gmail, Yahoo, and Microsoft, an 8.3% combined bounce rate sitting 66% above AWS’s 5% danger threshold, and a near-100% complaint rate at Yahoo signaling severe reputation damage.
The environment was operationally complex. Sixteen configuration sets spanned five sending platforms (SES API, CCAI, Sendy, Mailcoach, and EmailOctopus), nine sending domains needed individual authentication, and 10 of 16 config sets had no event destinations, leaving zero visibility into bounce patterns. Individual senders were hemorrhaging reputation, one at 32.6% bounce, another at 22.1%, while DMARC was missing on the primary domain and DKIM passed only 90.6% of the time.
The enterprise B2B context made everything harder. With 99.7% of sends targeting corporate domains, the firm faced Microsoft 365, Barracuda, Mimecast, and Proofpoint gateways whose filtering logic differs sharply from consumer ISPs, list aging was inevitable with executive turnover, and burst-then-silence sending looked like spam.
The AllCode solution
A Five-Phase Recovery Executed Without Pausing the Business
AllCode, an AWS Advanced Consulting Partner, implemented a comprehensive five-phase recovery strategy designed for enterprise B2B email infrastructure:
Phase 1: Emergency Stabilization (Week 1)
- Immediately paused the three highest-risk senders (32.6%, 22.1%, and 21.4% bounce rates)
- Deployed event destinations to all 16 config sets for complete bounce/complaint visibility
- Activated AWS SES suppression list and shared it with all sending platforms
- Implemented emergency daily send caps to prevent additional reputation damage
Phase 2: Infrastructure Hardening (Weeks 2-4)
- Fixed DKIM authentication failures across all sending domains
- Implemented DMARC records on primary and subdomain sending identities
- Configured SPF records for all subdomains (industrialtech, digital, etc.)
- Re-enabled VDM engagement metrics for sender reputation tracking
- Established per-sender list hygiene protocols with mandatory validation
Phase 3: Sender Rehabilitation (Weeks 4-8)
- Reduced highest-volume sender (313K sends/90 days) to 5K/day engaged-only lists
- Worked with individual senders to clean and segment lists by engagement history
- Established model sender workflows (achieved 35% open rate, 32% click rate, 0.11% bounce)
- Implemented mandatory warm-up cadence for reactivating paused senders
Phase 4: ISP Reputation Recovery (Weeks 8-16)
- Executed gradual volume ramp with Gmail, then Microsoft, then Yahoo
- Monitored corporate gateway responses (Microsoft 365, Barracuda, Mimecast, Proofpoint)
- Addressed transient bounce spikes from rate limiting with dedicated IP throttling
- Maintained zero complaint rate throughout recovery period
Phase 5: Governance & Sustainability (Ongoing)
- Established sender authorization protocols to prevent rogue send events
- Implemented hard daily send caps with mandatory list validation for batches >5K
- Set up automated monitoring with Google Postmaster Tools and Microsoft SNDS
- Trained client team on email list validation tools (ZeroBounce, NeverBounce, Kickbox)
- Delivered comprehensive operational documentation and runbooks
Architecture
Enterprise-Grade AWS SES Orchestration
Landmark Ventures now runs unified authentication, monitoring, and governance across a heterogeneous AWS SES environment spanning direct API, CCAI, Sendy, Mailcoach, and EmailOctopus. Every one of the 16 config sets carries event destinations, and DMARC, SPF, and DKIM are correctly configured across all nine sending domains and their subdomains.
The team navigated corporate gateways including Microsoft 365, Barracuda, Mimecast, and Proofpoint, whose sender-reputation and behavioral filtering differ from consumer ISPs. A suppression list of 11,600+ addresses now prevents repeat bounce events, while Google Postmaster Tools and Microsoft SNDS provide continuous reputation monitoring, and the CCAI config sets operate at 1.8% total bounce, best-in-class for B2B.
Results
Before and After
| Metric | Before | After |
|---|---|---|
| Inbox placement rate | 0% | ~95% |
| Combined bounce rate | 8.3% | 0.7% |
| Complaint rate | Near 100% (Yahoo) | 0.0% |
| Delivery rate | 91.7% | 97.3% or higher |
| AWS account status | Critical | HEALTHY |
Business impact
What the Recovery Restored
By August 2026 AllCode had turned a critical business risk into a sustainable operational advantage: bounce rate down 91%, a HEALTHY AWS account, and 88,395 sends per week at peak holding a sub-1% bounce rate.
%
Reduction in combined bounce rate
%
Inbox placement rate restored
%
Complaint rate held for 12+ weeks
%
Config sets with full event visibility
The engagement restored our ability to reach Fortune 500 decision-makers at a critical time for our business. AllCode’s systematic approach not only recovered our email infrastructure but established sustainable practices that continue to deliver results.