Blog/Migration
Migration · 4 Dec 2025 · 7 min

Running two marketing tools at once: how to plan the overlap

The fortnight where both platforms are live is the cheapest insurance in a migration and the easiest place to send everybody two of everything. What to switch when, and the three rules that prevent duplicates.

Two tools, one list, and a fortnight to get it right

Cutting over a marketing platform in one evening is possible and it is how most of the memorable failures happen. The alternative is a deliberate overlap: keep the old tool paid and live, move one thing at a time, and keep the ability to go back.

It costs one extra month's subscription. It buys you the ability to compare like with like, and a rollback that does not involve re-importing anything.

Rule one: every message type has exactly one owner

Write down which tool owns each message type, before anything is switched. The list is the plan, and it is what stops two systems being polite to the same customer.

A message type is owned by the old tool or the new one, never both, and ownership changes at a moment you choose rather than emergently.

  • Switch the old one off before the new one on, in that order, with a gap.
  • Confirm it is off rather than paused. Paused automations in several platforms resume on their own after edits or plan changes.
  • Keep the list visible where the whole team can see it. Most duplicate sends during a migration come from somebody helpfully switching something back on.

The order to move things in

  1. Suppressions first, before anything sends. Unsubscribes, hard bounces, complaints.
  2. One campaign from the new tool, to your most engaged few thousand. Proves authentication, rendering, links and tracking in one go.
  3. Welcome series, which only affects new subscribers.
  4. Post-purchase, which proves order events are arriving correctly — the dependency everything else rests on.
  5. Slow flows: win-back, replenishment.
  6. Browse abandonment.
  7. Cart recovery, last, because it has the most revenue attached and the least tolerance for a mistake.
The overlap is insurance, not indecision
The overlap is insurance, not indecision

Rule two: subscribe yourself on both sides

The only reliable duplicate detector is a mailbox. Before the overlap begins, put a real address into both systems, and a second address that exists only in the new one.

  • Watch for the same message arriving twice. This catches ownership mistakes within minutes rather than after a complaint.
  • Watch for nothing arriving, which is the other failure and is much easier to miss.
  • Check the footer, including which unsubscribe link is present. An unsubscribe that goes to the tool you are retiring will silently stop working when you cancel.

Rule three: compare on revenue per recipient, nothing else

Open rates are not comparable across tools — different image proxies, different bot filtering, different definitions. Click rates are comparable only if both are tracking the same way.

Revenue per recipient, on the same attribution window, computed from your own orders, is the one comparison that survives the move. Run the same campaign type from each tool a week apart to the same audience and compare that number.

Expect a difference. Investigate a large one before completing the migration, because after cancellation you cannot.

Ending the overlap

Do not let it drift. A three-month overlap is a migration nobody finished, and it doubles the number of places where a mistake can happen.

  1. Set the cancellation date at the start, and treat it as real.
  2. Before cancelling: export contacts, suppressions, campaign history, every template's HTML, screenshots of every automation, and your form wording.
  3. Remove the old provider's SPF include and DKIM records. Leaving them is a live authorisation for a service you no longer monitor.
  4. Keep the exports somewhere you will find them in two years, which is when somebody asks about a consent given in 2024.
Sources and further reading (4)
  1. Google — Email sender guidelines
  2. RFC 7208 — SPF
  3. RFC 8058 — One-click unsubscribe
  4. GDPR Article 7 — Conditions for consent

Checked on 23 September 2026. Provider prices, mailbox rules and legal guidance change — verify anything you plan to act on.

One comparison that survives the move

Revenue per recipient, from your own orders

Auralata computes revenue from WooCommerce orders rather than from its own click tracking, so the number you use to compare the old tool with the new one means the same thing on both sides.

Start now See how it works
Overlap · day 9ownership
Welcome seriesnew tool
Post-purchasenew tool
Cart recoveryold tool
Cancel on the 28th. Export everything before then.
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