Setting Up SMS Seed List Testing in Salesforce Marketing Cloud
How to send a test SMS to your Inbox Monster seedlist using Salesforce Marketing Cloud (SFMC) MobileConnect.
This article walks through a one-off seed list test — the setup you'll use each time you want to check how an SMS campaign lands with carriers before (or instead of) sending it to your full list.
Step 1: Download your Inbox Monster seedlist
In your Inbox Monster account, go to the Gear icon > Setup and Integrations, then download the most recent Seedlist - SMS.
This file contains the phone numbers Inbox Monster uses to monitor carrier placement. Currently, Inbox Monster tracks US and Canada carriers only.
Step 2: Add the seedlist to SFMC
In Contact Builder, create (or reuse) a sendable Data Extension — for example, IM_SMS_Seedlist — and import the numbers from your downloaded file. At minimum, include:
SubscriberKeyMobileNumber
Step 3: Confirm your seed numbers are opted in
This is the step most tests get stuck on: MobileConnect will not deliver an SMS to any number that isn't opted in to your specific Short/Long Code and Keyword — even if the number is sitting correctly in your Data Extension.
If your seed numbers aren't already opted in:
In Contact Builder > Imports, create an import pointed at your seedlist Data Extension.
Agree to the Opt-In Certification step.
Choose the Short/Long Code and Keyword your test message will send from.
You only need to do this once per seedlist — not before every test.
Step 4: Send your test message
Add your sending number(s) in Inbox Monster's Setup and Integrations first, so results are properly monitored.
Then, in SFMC:
From Automation Studio: create a one-time Send SMS activity, using
IM_SMS_Seedlistas the audience.From Journey Builder: use
IM_SMS_Seedlistas a one-time Data Extension entry source for a simple, single-send journey.
Either way, keep the message content identical to what you'd send in production — no dynamic content, since variations can cause incomplete or duplicated reporting in Inbox Monster.
Step 5: Check your results
Head to SMS > Delivery in your Inbox Monster platform. Results typically populate within a few minutes and include:
Carrier placement (US and Canada)
Content analysis (spam word detection, unsubscribe mechanism check, link reputation)
Device preview (iOS/Android, Locked/List/Message views)
Troubleshooting
No results showing up: confirm your sending number is added in Inbox Monster and formatted correctly — long codes need a leading "+", short codes don't.
Some seed numbers didn't receive the message: check opt-in status (Step 3) first — this is the most common cause.
Reporting looks incomplete or duplicated: make sure your test message doesn't include dynamic content.
Still stuck? Reach out to your dedicated Inbox Monster support contact — we're happy to help.
Sending seed tests often and don't want to re-upload your list every time? SFMC can automate keeping this Data Extension current and opted-in — ask your Inbox Monster contact if you'd like a walkthrough.
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