Sending an SMS in K3X happens in two places:
From a lead's profile — the most common path. Open any lead, click the SMS icon, type, send.
From AI Chat — ask in plain language ("text Brian asking if 3pm works") and approve the draft.
Both routes use the same underlying number and show up on the same lead timeline.
Before you start.
You need a phone number attached to K3X. If you don't have one yet, see Buy or port a phone number into K3X.
For US/Canada SMS at any meaningful volume you need either A2P 10DLC registration (for local numbers) or Toll-Free verification (for toll-free numbers). Without one of these in place, carriers will silently filter most messages — they'll show as "sent" in K3X but never arrive.
The recipient must not be on your opt-out list (anyone who replied STOP to a previous message from you).
Walkthrough: send an SMS from a lead.
Open the lead. The right-hand side panel shows their phone numbers.
Click the SMS icon next to the mobile number you want to text. (Icon is greyed out if the number isn't mobile-capable — K3X looks up line type when the contact is created.)
A composer slides in from the right. Type your message. Character count and segment count display below the field (1 segment = up to 160 chars in standard GSM, 70 chars if you use emoji).
Pick the from number if your team has more than one. K3X defaults to the number assigned to you, or the lead's owner.
Hit Send.
The message threads onto the lead's activity feed immediately, with a status pill that updates as the carrier responds: queued → sent → delivered (or failed with a reason code).
Walkthrough: send via AI Chat.
Open AI Chat from the sidebar. Type something like "text Brian Chen asking if 3pm today still works for the demo." Chat looks up the lead, drafts the message, and shows you a confirmation card with the recipient, the from number, and the draft body. Edit if you want, click Send, and the same threading happens on the lead.
AI Chat never sends SMS without your explicit approval (unless you've opted into autosend on a specific Agent — see A quick tour of the four main tabs).
What happens when they reply.
Inbound SMS lands on the same lead's timeline as a reply. You'll get an in-app notification (and a desktop notification, if enabled). You can reply right from the activity feed, or open the composer for a full thread view.
If the inbound number doesn't match an existing lead, K3X creates a new lead automatically and you'll see it in your inbox.
Common gotchas.
"Sent" but not "delivered." Usually carrier filtering. Most common cause: your 10DLC or TFV registration isn't active yet. Check Settings → Phone Numbers → [number] → Compliance.
Failed with code 21610. The recipient previously replied STOP. They have to text START to your number to opt back in — you can't override this from K3X.
Failed with code 30007. The carrier flagged your message as spammy. Re-read the message: missing sender identification or opt-out language are the usual culprits.
International number. Sending to +44 or other non-NANP numbers requires international SMS enabled on your account, plus often a registered Sender ID for the destination country. See International SMS.
Image or attachment. SMS doesn't carry images — you need MMS, which has its own rules. See MMS.
Next: Place your first call from K3X →
