You can view all opt-outs/unsubscribes by going to Subscribers > View All > + Filter > Choose SMS Status > Opted Out > Apply.
To create a downloadable CSV of your opt-outs, click Actions > Export on the far right. Your exported file will be shown at the top right of your screen within a few seconds.
To see who has opted out of a specific message, select the message > Scroll down to Message Activity > Select Opt-outs. This will show you who opted out of texts in response to receiving that message.
Have more questions? Reach out to our team in the chat! We'd love to help.