With a Sender Authentication Package (SAP) and dedicated IP address, maintaining a minimum volume (around 250,000 messages/month) is critical to building and maintaining a healthy sender reputation. If the volume drops too low, deliverability could be negatively affected.
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Exact Extracts from Salesforce Documentation:
Source: Salesforce Help - Dedicated IP Warming and Maintenance
# "To maintain a strong sending reputation on a dedicated IP address, customers should send a minimum of
250,000 emails per month."
Source: Salesforce Marketing Cloud Implementation Guide - Sender Authentication Package
# "Dedicated IPs provided with SAP require consistent, high-volume sending for optimal performance."
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Explanation
To target all customers who have registered to receive push notifications, Northern Trail Outfitters can use two ways to create this segment:
Using Mobile Studio, create a Mobile Push Filtered List then filter onthe MobilePush Demographics attribute group. This is a user-friendly tool that allows marketers to segment their mobile push audience based on criteria and conditions without coding.
Using Automation Studio, query the _MobilePushDemographics Data View andsave this to a data extension. This is a more advanced tool that allows marketers to segment their mobile push audience using SQL queries and data views.
Using Journey Builder or Contact Builder are not ways to create segments for mobile push audiences, asthey are used for different purposes. References:
https://help.salesforce.com/s/articleView?id=sf.mc_moc_create_a_filtered_list.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.mc_as_query_activity.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.mc_as_data_view_mobilepushdemographics.htm&type=5

* Text Response templates allow recipients to reply to an SMS message, and MobileConnect can handle that reply.
* Data Capture templates allow you to store the SMS reply into a specific Data Extension for further processing, especially when using AMPscript.
Info Capture is used for form-style step-by-step conversations, not one-shot responses. Outbound is simply for sending SMS messages, without expecting or processing replies.
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Exact Extracts from Salesforce Documentation:
Source: Salesforce Help - MobileConnect Message Templates
# "Use Text Response to receive responses from subscribers and store those responses in a data extension with Data Capture templates." Source: Salesforce Help - Data Capture for SMS Responses
# "Data Capture templates in MobileConnect enable collection of information from subscribers directly into a data extension for further use."

Explanation
To report on 'Not Sent' contacts in Journey Builder, Northern Trail Outfitters should use the standard report
'Subscribers Not Sent to'. This report shows how many contacts were not sent an email due to various reasons, such as unsubscribes, bounces, duplicates, or errors.
References:https://help.salesforce.com/s/articleView?id=sf.mc_rn_subscribers_not_sent_to_report.htm&type=5