SMS Messages
Send transactional and marketing SMS, and follow each message's delivery live.
The SMS log shows every message your workspace has sent or received, live — queued, sent, delivered, or failed, with the carrier's failure reason when there is one. Each row opens a per-message page with the sender number, segments billed, and the carrier's event timeline. Billing is per segment: 160 GSM-7 characters fit one segment (153 each when a message spans several); Unicode messages fit 70/67. The composer shows the segment count as you type. Sending needs a paid plan. New to the channel? Start with SMS vs email.
Marketing SMS is held to a stricter bar than email: the recipient must have prior express consent on record, and sends respect recipient-local quiet hours (a marketing message queued at midnight is deferred to the morning window, never dropped and never sent at 2am). Transactional messages — receipts, alerts, verification codes — are not window-gated.
STOP always wins
When a recipient replies STOP, the carrier and Unitpost both record the opt-out immediately. Further sends to that number are suppressed on the SMS channel — it never touches their email subscription, and vice versa.
Replies
Your toll-free, 10DLC and Canadian numbers receive replies; Sender IDs are one-way (the Phone numbers page marks which is which). A reply shows in the log as Inbound with the text, the number it came from, and a link to your message it answers when the carrier says which. Reply opens the composer addressed to that person from the same number. Each text you receive costs 1¢ in the US and Canada, whatever its length; the message page shows what it was billed. Each one also fires the sms.received webhook, which is how an app or an AI agent answers in its own words; see the SMS API's Start page.
Keyword replies are handled for you. STOP, CANCEL, END, QUIT, UNSUBSCRIBE and the other opt-out words opt the number out; START and UNSTOP opt it back in; HELP and INFO get your registered help text. Only a text that is just the keyword counts, so "please stop texting me" is a normal reply. A one-word answer such as "Cancel" is an opt-out, so phrase questions so that a single word answer can't be one ("Reply 1 to keep, 2 to move").