---
title: "Set Up a TMID for Transactional Messages"
slug: "add-a-tmid-to-messages"
description: "Set up a group in Mapp Engage so every transactional message gets a unique TMID, including the mode settings and an example pattern."
status: "update"
updated: 2026-11-06T16:01:02Z
published: 2026-11-06T16:01:02Z
canonical: "docs.mapp.com/add-a-tmid-to-messages"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mapp.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Set Up a TMID for Transactional Messages

## Goal

Set up a group so that Mapp Engage adds a unique Transactional Message ID (TMID) to each message. With a TMID, you can track every message individually. For the concept and the TMID modes, see [Transactional Messages](/v1/docs/transactional-messages).

You only need this setup if Mapp Engage creates the TMID. If your external system creates a unique TMID and sends it with the API call, leave **Transactional Message Mode** on **Off**. See [Sending Transactional Messages (API)](/v1/docs/send-transactional-messages-api).

---

## Procedure

1. Go to *Audience > Group Management > Groups*.
2. Open the group and click the **Sendout Options** tab.
3. Expand the **Transactional Messages** section.
4. From **Transactional Message Mode**, select one of the following:
  - **On**: Mapp Engage creates a TMID for every sendout in the group. A TMID sent with an API call is replaced.
  - **Optional**: Mapp Engage creates a TMID only for sendouts that do not have one. A TMID sent with an API call is kept.
5. In the **Pattern for the TMID** field, enter a pattern that creates a unique ID for each message. To insert attributes, click *Personalisation*. If the pattern does not create a unique ID, you cannot track the messages individually.
6. Click **Save**.

### Example Pattern

The following pattern combines the contact ID, the message ID, and the current time in UTC:

```pgsql
u=<%${user['PK']}%>m=<%${message['PK']}%>t=<%${ecx:formatDate(ecm:addInterval(date.today, '-0d'),'yyyy-MM-dd\'T\'HH:mm:ss.SSS\'Z\'', ecm:timeZone('UTC'),'', false)}%>
```

- `u=&lt;%${user['PK']}%&gt;`: the contact ID
- `m=&lt;%${message['PK']}%&gt;`: the message ID
- `t=&lt;%${ecx:formatDate(...)}%&gt;`: the current date and time in UTC, in ISO 8601 format. `ecm:addInterval(date.today, '-0d')` keeps the current date. Change the interval if you need a different date.

Because the TMID combines contact, message, and sendout time, it is unique for every sendout.

## Related

- [Group Creation: Sendout Options](/sendout-options-tab.md)