Classic dilemma, but haven't found any clear best practice.

We have Email campaigns to encourage subscribers to Opt-in to SMS.

Something along - Text "JOIN" to XXXXX.

When someone texts JOIN, we see them in Mobile Connect, but the Contact Key is, as expected, the Mobile Number.

Assuming we already have the Mobile number on either Salesforce_Contact or on another DE, how do we bridge the data gap? (i.e. how can we use the Salesforce Contact ID (current SubscriberKey on Push and Email) - implemented also for SMS?

In other words what is the correct way to associate this Contact with an Existing contact ?

Thanks for your help!

2 Answers 2


I'm working on a similar challenge and so far the process I'm looking at is much like how Salesforce manages duplicate records. In SFMC you'll have to build an automation that will look for recent mobile connect opt-ins and compare that with your existing Salesforce contacts. When you find matches, you'll need to opt the Salesforce contact into the matching keyword using an Import Mobile Contacts activity, then delete the duplicate record using an SSJS script activity or add them to a data extension that gets regularly deleted from Contact Builder. Unfortunately the Subscriber Key cannot be modified or it'd be a simpler process.

This trailhead may be of some use: https://trailhead.salesforce.com/content/learn/modules/mobile-contact-management

  • Thanks @Matthew, yeah, I imagined some kind of workaround like this, just disappointed there is nothing out-of-the-box to handle these. So, eventually you'd align with the Salesforce SubscriberKey, and delete the MobileNumber as Key, correct? Once associated with the SF SubscriberKey, will this work the next time the Client replies to an SMS? (Next Keyword / info Capture message type)
    – LimeWeb
    Nov 20, 2020 at 15:16
  • Anytime there's a reply with either info capture or next keywords you should be fine, but I'm not sure how it works when that subscriber wants to opt in to a new keyword via SMS. Report back with your findings! Nov 21, 2020 at 17:00

I am not sure if this is the right way, but what I can think of a work around something like this.

  1. Import the customers of your target DE, with their mobile numbers in Mobile Connect. Do this before sending the email.
  2. While importing, you can opt out everyone.

When the user subscribes using the text message, since the subscriber key associated with that mobile number is already present in the system, it will just opt in. And the subscriber key will be there in place.

  • How does that solve duplicate scenarios of opting in via SMS Keyword/Shortcode combos for subscribers that you don't yet know about? How do you pair a email subscriber and a mobile subscriber in multi channel journeys this way? Nov 19, 2020 at 20:42
  • I assumed in the question that the subscribers are known and the mobile numbers are already present on a DE. Nov 20, 2020 at 8:01
  • Interesting thought, thank you Swati. Though Matthew brings up a valid point. What if they opt in with a different number after they received the incite to reply to a SMS?
    – LimeWeb
    Nov 20, 2020 at 15:21
  • Agreed, but what I assumed in your question, that you already have the mobile number Nov 20, 2020 at 15:46

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