How to create a segment based on property value that hasn't been collected yet?

Hi ​@Kirsten Thompson,

Sorry it has taken me so long to get back to you. I’m glad to hear that you can pull lists of SMS subscribers.
I’m not sure if this is the “best” idea, but I would create a separate field for mobile numbers.
- First, create the field in one profile - I typically create the field in my own profile when adding something new. Whatever you name it, know that you have to use the EXACT format if you want to pull it into an email, or update it, etc. For example, if it’s capitalized, it should always be capitalized. I’m not sure if this field should be a number or text field; text field seems to be more flexible in my opinion.
-Create a blank list (can be deleted later).
-Export all the SMS subscribers (and non-subscribers, if you want) and include the phone number field.
-Import all the records you just exported to the blank list, and map the existing phone numbers to the new mobile number field.
-Once done, you can delete the list (it only deletes the list, not the profiles in the list) if you want.
-Then you can build a segment where the new mobile number field doesn’t have any numbers, as Dov mentioned above. Or, since it is a custom property, you can build a segment where the new field is not set.
Hope this helps, let me know if I can explain anything further!