# Send SMS by email

Users on your Iflow account can send an SMS by sending an email. The email's body becomes the text message.

## Before you start

The email must come from an address that belongs to a [user on your account](/docs/account/users/). Emails from any other address aren't recognised and aren't sent.

## Addressing

Send the email to the mobile number at the gateway domain.

<!-- NEEDS CONFIRMATION: the gateway domain for Iflow accounts. The source page used text.diarybook.com. -->

- **Mobiles in the Republic of Ireland:** start with `08` followed by the rest of the number. To text `0870000000`, send the email to `0870000000@text.diarybook.com`.
- **Mobiles in other countries:** use the international format without the `+`. To text the UK mobile `07800000000`, send the email to `447800000000@text.diarybook.com`.

## Message length

A single text message holds up to 160 characters, including spaces. A longer email is sent as two or more parts that are joined back together on the recipient's phone, and each part is charged. See [SMS message parts](/docs/reference/sms-message-parts/).

To cap the number of parts, use `restrictSize` in the subject line (below). With `restrictSize=1;` only the first 160 characters are sent.

## Subject line settings

The subject line can carry settings that change how the message is sent. Write each one as:

```
parameterName=parameterValue;
```

> [!NOTE]
> There must be no spaces, and each setting must end with a semicolon.

| Name | Value | What it does |
|------|-------|--------------|
| restrictSize | Maximum parts | Limits the number of parts the message is sent in |
| senderId | Sender ID | Chooses which of your sender IDs to send from |
{.table}

For example, if your account has `SHOP` as an approved sender ID, put `senderId=SHOP;` in the subject. Without it, the message is sent from your account's default sender.

Your account can instead be set up to include the subject line in the text. The first line of the message is then the subject, followed by the body of the email.

## Securing the gateway

For extra security, add a gateway key header to every email you send. See [Gateway keys](/docs/email-to-sms/gateway-keys/).

## Related

- [Gateway keys](/docs/email-to-sms/gateway-keys/)
- [About sender IDs](/docs/sender-ids/about-sender-ids/)
- [SMS message parts](/docs/reference/sms-message-parts/)

---
Source: https://iflow.net/docs/email-to-sms/send-by-email/