A text messaging subscriber is a user who prefers or can only read emails sent to them in plain text. As detailed by previous respondents, an SMS subscriber is someone who specifically requests to receive SMS. … When an ESP (Email Solution Provider) is used to send text emails, opens and clicks can be tracked.
Your TextNow number is the number you’ll want to give your friends and family to call and text you, and it’s the number your calls and texts will come from. … This number is used to connect your phone to the network. Text Mail Subscriber
They choose not to receive HTML or rich text emails for an added level of privacy and security for tracking web beacons if they open or click on emails. When you send emails to these people, it is advised to use plain text to make the emails easier to read as one of your favorite customers.
As detailed by previous respondents, an SMS subscriber is someone who specifically requests to receive SMS.
As noted, emails sent through email and ESP clients are in MIME or multipart format which supports different types of content and multipart messages and determines which format to display for a given recipient.