What’s the best way to test before and after an MBP update?

Here's a scenario that trips up a lot of senders. You notice your inbox placement dipping after a suspected MBP update. But you didn't record what your numbers looked like before it hit, so you have nothing solid to compare against. That's the trap.

Good before-and-after testing comes down to one principle: keep everything except the MBP's behavior the same. Same content, same sending volume, same time of day, same seed list. If you change two things at once, you can't tell which one moved the needle.

Before the update (your baseline)

Set up a consistent send to your seed accounts at least two to four weeks before any suspected update window. You want enough data points to see your normal range, not just a single snapshot. Record inbox placement rates, spam folder rates, delivery timing, and any tab routing (like Promotions vs Primary in Gmail). That's your baseline.

If you don't have a seed list yet, now is the time to build one. Grab accounts across the major mailbox providers you care about: Gmail, Outlook, Yahoo Mail, and iCloud Mail at minimum. Tools like Mailtrap can help, or you can maintain your own seed accounts manually.

After the update

Send the same test message (or a structurally identical one) to the same seed accounts, within a similar time window. Wait at least 24 to 48 hours before drawing conclusions. Filter changes sometimes take time to propagate fully, and a single send can be noisy.

Compare inbox placement rate, spam rate, and timing side by side. A drop in inbox rate or a spike in spam at one specific provider points directly at that provider's update. If you're seeing the same pattern across all providers, it's more likely a change on your end or a reputation shift rather than a single MBP update.

What to track

• Inbox vs spam placement rate per provider
• Tab routing changes (Promotions, Updates, etc.)
• Delivery speed (time from send to delivery)
• Any new bounce codes or error messages you weren't seeing before

Document everything. A simple spreadsheet with date, provider, placement result, and notes beats trying to remember what changed three weeks later.

Now once you have the before and after numbers, you can measure whether that drift is ongoing or a one-time adjustment. That context matters a lot for deciding what (if anything) to change.

If you're not sure what your current placement looks like across providers, our SOS hotline is free and we're happy to help you think through a testing setup that fits your volume.