6M Contacts, One Inbox

How We Scaled Salesforce Marketing Cloud


Lessons learned from building safe, compliant, high-volume campaigns. Domain reputation, suppression logic, throttling, and gradual list warming all matter. Here's how I approached it.

P.S. If you’re only sending 100k–500k emails, Excel is fine! Here's a small-scale guide.

Start Small, Build Confidence

When you’ve never sent millions of emails, start tiny. I kicked off with a 5% segment. Track opens, clicks, bounces, complaints. Anything off? Stop, fix, retry. Step 2 was 25%, then full send.

This approach mirrors defensive SQL patterns. Think of each step as a safeguard. Even with millions of contacts, small tests prevent disaster.

Domain Reputation

Monitor reputation at each stage. Use separate sending domains for high-risk campaigns. Alerts for bounce spikes? Critical. SFMC reports and third-party monitoring tools helped me catch issues before they escalated.

Suppression Logic & Throttling

Key takeaway: never send to everyone at once. Layered suppression lists - unsubscribes, hard bounces, do-not-contact - plus send throttling, ensured we didn’t overload inboxes or spam filters. Even with 6M contacts, proper throttling kept engagement healthy.

Gradual List Warming

Start small. Increase slowly. Watch metrics obsessively. This prevents blacklisting and protects domain reputation. I’ve written about SQL techniques to pre-filter and validate lists in SQL Patterns for Email Segmentation.

Monitoring and Feedback Loops

Real-time dashboards for bounces, unsubscribes, complaints, and engagement. Alerts tied to thresholds. On the next day, if metrics spiked, I’d pause and dig in. Over time, tweaks improved deliverability and engagement simultaneously.

[Segmented List] --> [Validation Checks] --> [Throttled Sends]
      |                   |                        |
      v                   v                        v
[Suppression Filters]   [SQL Checks]      [SFMC Triggered Send]
  

Next steps: apply the same defensive mindset upstream. Tealium, Segment, or Hull pipelines feed validated, enriched data into SFMC. Check out Tealium vs mParticle for the CDP side of things.

Takeaways: