Message Log
Messaging is included on Essentials and Production Pro.
Go to Messaging, then Message Log to see your recent emails and texts. Use the All, SMS and Email tabs to filter.
The Recipients column shows how many people each message went to and what happened:
sent: delivered to the email or phone provider.
unsubscribed: skipped because the person unsubscribed or replied STOP.
out of credits: skipped because you ran out of message credits.
failed: the provider couldn't deliver it, often because of a bad email address or phone number.

