Every Subscriber in Clearstream has a status. The status of most Subscribers will be "opted-in", but there are three statuses that Subscribers can have: Opted-In, Opted-Out, Inactive. You will only be able to text Subscribers who are Opted-In (aside from replying to an incoming message or sending an automated response).
If you're planning to communicate with people on an ongoing basis (announcements, reminders, etc) you'll need these Subscribers to be opted in.
There are four primary ways people can opt-in to your account:
Importing a CSV file from the Subscribers page.
Texting in with a Keyword.
Signing up through a Website Form.
Things to note:
After someone opts out, they will no longer receive your messages.
If someone has accidentally opted-out, they can opt themselves back in by texting in with a Keyword or using a Website Form.
Subscribers who are opted-in can be copied and moved into other Lists.
If you have any questions about this or need help opting Subscribers in, reach out to our Support team, we're happy to help.