DTC Newsletter / Senior Website and Email Operations Manager / 2021 – 2024
ESP migration and deliverability rescue
Sender score in the low 20s, inbox placement collapsing, and the cause was not the content.
The read
Open rates were falling. Spam placement was rising. The instinct in the room was to fix the content - cleaner subject lines, better segmentation, fresher copy.
I looked at the infrastructure instead. The problem was not what we were sending. It was how we were sending it. DTC was on a shared IP inside ActiveCampaign. Other senders on that IP were damaging the shared reputation and there was nothing we could do about it from our end. A dedicated IP would have solved it, but it was not in the budget.
The read: the deliverability problem was not fixable within the current platform. The only real fix was a migration.
The decision
Move to Campaign Monitor where we could get a clean sending environment, warm a new domain properly, and own our reputation from the ground up.
This was not just an ESP swap. It meant migrating 200K+ subscribers, rebuilding every automation, reconfiguring authentication, and warming the new domain before a single campaign could go out. The newsletter ran 5x a week. There was no pause button.
The metric I chose
Sender score. Not open rate, not click rate. Those were already broken signals because the deliverability problem was suppressing them. The underlying reputation score was the leading indicator. If that moved, everything downstream would follow.
Secondary: spam placement rate via GlockApps. Inbox vs. spam across major providers was the real-time read on whether the migration was working.
The build
Built the migration in phases so the newsletter never stopped. Configured DKIM, SPF, and DMARC on the Campaign Monitor domain. Executed a warming sequence from zero before scaling to full list volume. Rebuilt every automation in Campaign Monitor from scratch.
Segmented the list before the first send: active, inactive, and zombie segments. Started warming with the most engaged segment only and expanded volume as sender score climbed. Used ZeroBounce to clean the list before migration, GlockApps to monitor inbox placement throughout, and Litmus for rendering checks across email clients.
Built ongoing deliverability SOPs so the team had a defined response protocol if scores started dropping again.
20s → 90+
Sender score
200K+
Subscribers migrated
The sender score did not just recover - it stabilized above 90 with the SOPs in place. The diagnostic was right: the problem was never the content. It was the infrastructure. Once the infrastructure was clean, the content had a fair chance to perform.
Tech
Campaign Monitor, primary ESP post-migration
ZeroBounce, list hygiene and bounce management
GlockApps, inbox placement monitoring
Litmus, rendering and spam filter testing
DKIM / SPF / DMARC, email authentication
Miguel N. Monzones
Vancouver, BC, Canada
