> For the complete documentation index, see [llms.txt](https://docs.limecall.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.limecall.com/virtual-numbers/sms-and-messaging.md).

# SMS & messaging

Send and receive text messages from your numbers.

## What you need

**A number with SMS capability.** Not all numbers have it — check capabilities before buying. See [Buy a number](/virtual-numbers/buy-a-number.md).

**Carrier registration, for US recipients.** Required before you can reliably text US numbers. See [US carrier registration (10DLC)](/virtual-numbers/us-carrier-registration.md).

## Sending a message

From the **Inbox**, open a conversation and reply, or start a new message to a contact. Messages are threaded with everything else from that person — calls, WhatsApp, email — on one timeline.

## Receiving

Inbound messages arrive in the **Inbox**. They can be answered by a person, or by your AI receptionist if you have enabled the text channel. See [Text messages](/ai-receptionist/text-messages.md).

## Templates and signatures

Set message templates and signatures under **Settings → Inbox** and **Settings → Messaging**, for the replies you send repeatedly.

## Auto-replies

Simple trigger-based automatic replies are configured under **Settings → Messaging** — for example, an acknowledgement to a message received out of hours.

These are fixed text, not the AI. If both are enabled, make sure they are not both responding to the same message.

## Campaigns

To message many contacts at once, use **Campaigns** rather than the Inbox. See [Campaigns](/inbox-and-leads/campaigns.md).

## Deliverability

Texting is heavily filtered by carriers. What gets messages delivered:

* **Register properly.** Unregistered US traffic is blocked. This is not optional.
* **Identify yourself.** Say who you are in the first message; a message from an unknown number with no sender name looks like a scam.
* **Include opt-out instructions** on bulk messages.
* **Avoid link shorteners.** Public shorteners are strongly associated with spam. Use your own domain.
* **Send at reasonable hours** in the recipient's time zone. Many jurisdictions restrict the hours for commercial messages.

{% hint style="warning" %}
Carriers filter silently. A message can be accepted by the API, reported as sent, and never delivered. If delivery rates look wrong, check your registration status first.
{% endhint %}

## Opt-outs

Replies of STOP, UNSUBSCRIBE, CANCEL and similar suppress the contact automatically, and no further messages are sent to them.

This is a legal requirement in most markets. Do not attempt to work around it — the penalties are significant and the suppression protects your numbers' reputation.

## MMS

Some numbers support picture messaging. Check capabilities before relying on it, and note MMS is not universally supported outside North America.

## Costs

Messages are charged per segment. A long message is split into several segments and billed accordingly, and using emoji or other non-GSM characters reduces the characters per segment considerably — a single emoji can nearly halve it.

See [Usage & credits](/account/usage-and-credits.md).

## If messages are not arriving

See [Texts are not being delivered](/troubleshooting/sms-not-sending.md).