AI SDR & AI Outbound
AI-powered sales & outreach tools
Platforms that use agents and automated workflows to run large-scale outbound email and multi-channel prospecting for B2B sales teams.
Case Study
AI Sales Platform Deliverability Transformed
How we recovered inbox placement from 43% to 81% for an AI SDR tool, saved $840K in at-risk ARR, and built robust email infrastructure for multi-tenant SaaS at scale.
Book a Free Deliverability AuditThis case study represents a composite of multiple client engagements to protect confidential client information while accurately reflecting the outcomes and methodologies Postbox Services delivers for AI-native, high-volume platforms.
Who We Help
We work with fast-growing products where email deliverability is critical to the value they deliver.
Sales Engagement
Sequences & multi-channel outreach
Products that orchestrate email sequences, follow-ups, and prospect journeys across different mailboxes and domains at scale.
Demo & GTM Tools
Demo & asset-driven workflows
Platforms that rely on email to deliver interactive demos, trial experiences, or content that sales teams send at high volume.
The Challenge
A rapidly growing AI sales platform powering automated outbound for 150+ B2B customers, sending millions of emails monthly, watched its inbox placement rate fall from 78% to 43% in three weeks - and customer confidence fell with it.
"Our emails suddenly dropped into spam."
"One customer tanked the reputation for everyone."
"Gmail throttling is killing our outbound."
"Warmup breaks every time we increase volume."
"Demo emails aren't getting opened anymore."
Root Causes Identified
Multi-tenant deliverability failure
One customer's aggressive sending pattern tanked domain reputation for all users on shared infrastructure.
Automated outbound throttling
Volume ramping too quickly without proper warmup protocols caused Gmail to severely limit delivery.
Infrastructure gaps
No domain rotation strategy, insufficient monitoring, and reactive (not proactive) reputation management.
Scaling constraints
Adding new customers required manual provisioning and created single points of failure.
Business Impact
23%of enterprise customers threatened to leave within 30 days
$840KARR at risk from affected accounts
60+ hrsper week spent firefighting instead of building features
The Solution
A comprehensive deliverability transformation and ongoing infrastructure management program, designed for multi-tenant SaaS environments running automated outbound email at scale.
1
Phase 1: Emergency Stabilization
Weeks 1-2- Deep infrastructure audit across all sending domains and mailboxes
- Identified 12 domains with critical reputation issues requiring immediate quarantine
- Emergency domain rotation to isolate problem accounts
- Real-time monitoring for domain and IP reputation scores
- Complaint feedback loops established with major ISPs
- Temporary sending pools to stabilize delivery for high-value customers
2
Phase 2: Infrastructure Rebuild
Weeks 3-5- Segmented domain pools by customer risk profile
- Domain rotation logic to prevent single-customer contamination
- Separate warmup and production pools for controlled scaling
- Sourced and provisioned 500+ compliant Gmail and Outlook mailboxes
- Automated warmup engine with progressive volume ramping
- DKIM, SPF, and DMARC configured with full alignment across all sending domains
3
Phase 3: Operational Management
Weeks 6-8 & ongoing- Daily warmup execution and mailbox health monitoring
- Proactive blocklist and spam trap detection
- Weekly inbox placement testing via seed lists
- Complaint and bounce rate monitoring with automated alerts
- Monthly deliverability optimization reviews
- Customer onboarding protocols and engineering team training
Results & ROI
+38ppInbox Placement ImprovementFrom 43% to 81% average
$840KARR RetainedSaved all at-risk accounts
74%Support Ticket ReductionEmail-related complaints
92%Engineering Time SavedFrom 60 hrs/week to under 5
+34NPS Point IncreasePlatform-wide customer score
40+New Enterprise CustomersOnboarded in 90 days
→
Successfully onboarded 40+ new enterprise customers in 90 days post-stabilization
→
Scaled from 2.5M to 6.8M emails per month without infrastructure incidents
→
Unlocked $2.1M in new ARR that was previously blocked
→
Engineering team freed up from 60 hours/week to under 5 hours/week on email issues
What the Team Said
"Before Postbox, our engineers were constantly pulled away from product development to fix email fires. Now they can focus on building AI features while deliverability just works in the background."
- VP of Engineering
"We went from defensive conversations about why emails weren't delivering to proactive discussions about scaling volume. The confidence our customers have in the platform completely changed."
- Head of Customer Success
"Email deliverability used to be a deal-killer in enterprise sales conversations. Now it's a competitive advantage. We can confidently commit to inbox placement SLAs."
- Chief Revenue Officer
Technical Implementation
📤
Sending Layer
- Google Workspace + Microsoft 365 + AWS SES for SMTP relay
- Custom domain pool management system
- Automated mailbox provisioning and rotation
- Multi-tier warmup engine (conservative, moderate, aggressive profiles)
📡
Monitoring & Observability
- Real-time reputation scoring for domains and IPs
- Automated blocklist monitoring (100+ lists checked hourly)
- Seed list testing across Gmail, Outlook, Yahoo, and 15+ ISPs
- Complaint feedback loop integration with major providers
🧱
Multi-Tenant Isolation
- Customer risk profiling (sending patterns, complaint rates, engagement)
- Dynamic domain assignment based on risk score
- Automatic quarantine triggers for problematic accounts
- Separate infrastructure for trial vs. paid customers
📘
Operational Playbooks
- Customer Onboarding Protocol: pre-flight checks before enabling sending
- Incident Response Playbook: rapid triage for sudden deliverability drops
- Scaling Checklist: requirements for increasing volume by 50%+
- Quarterly Health Review: proactive optimization recommendations
Key Success Factors
⚡
Speed of Response
Emergency fixes deployed within 72 hours of engagement. Full infrastructure rebuild completed in 5 weeks, not 5 months. Continuous improvements shipped weekly, not quarterly.
🎯
Domain Expertise
Deep understanding of multi-tenant deliverability challenges, experience with AI-powered sending platforms, and relationships with ISP teams for rapid issue escalation.
🧰
Full-Stack Ownership
Single point of accountability from infrastructure to daily operations. No finger-pointing between vendors. Proactive monitoring caught problems before customers noticed.
🤝
Partnership Approach
Weekly sync with the engineering team during buildout, knowledge transfer so the internal team understood the system, and collaborative problem-solving rather than black-box delivery.
Long-Term Partnership
In the 9 months following infrastructure stabilization:
→
Scaled from 6.8M to 18M emails per month
→
Maintained a consistent 78-83% inbox placement rate
→
Added 120+ new customers without major incidents
→
Achieved SOC 2 compliance (email infrastructure components)
"Postbox didn't just fix our deliverability crisis - they transformed email from our biggest operational headache into a competitive advantage. The infrastructure they built and manage for us has been rock-solid even as we've tripled our sending volume. More importantly, their team acts as a true partner. They understand our business, not just the technical details."
Lessons Learned
For AI-Powered Sales Platforms
- Don't wait for a crisis: proactive infrastructure management is 10x cheaper than emergency recovery
- Multi-tenant isolation is critical: one bad actor can tank reputation for hundreds of customers
- Warmup is non-negotiable: aggressive ramping will burn domains faster than you can replace them
- Monitoring must be real-time: deliverability issues compound hourly, not daily
- Offshore what's not core: your engineers should build AI features, not manage mailbox rotation
For Platform Engineering Teams
- Deliverability is a full-time job: it requires dedicated expertise, not part-time attention
- ISP relationships matter: escalation paths with Gmail/Outlook teams save weeks during incidents
- Infrastructure must scale ahead of demand: you can't add domains and mailboxes on-demand without warmup
- Compliance is mandatory: DKIM, SPF, and DMARC aren't optional for serious platforms
- Customer education prevents problems: most issues come from users who don't understand email limits
About This Engagement
Services delivered: emergency deliverability recovery, multi-tenant infrastructure design and deployment, mailbox pool sourcing and management, daily operational management, strategic deliverability consulting, and engineering team training.
Ready to Strengthen Your Platform's Deliverability?
If your AI-powered platform, sales engagement tool, or multi-tenant outbound product is experiencing similar challenges - or you want to avoid them entirely - let's talk. We'll review your current setup, highlight risks, and outline how to support your next stage of growth.
Book a Free Deliverability Audit