# Before Migrating from 20.04.xx

Migrating from any version in the **20.04.xx** family is a special step because Exchange Connector moves from the legacy dedicated installation to the new vtenext module/extension structure.

## Migration paths

- **20.04.xx → 24.08**;
- **20.04.xx → 26.04**.

In both cases, the Exchange module registration step must be performed once. If Exchange Connector is already on version 24.08, use the standard upgrade procedure described in [Upgrading from 24.08 to 26.04](https://manual.vtenext.ch/books/exchange-connector-vtenext-Hfx/page/upgrading-from-2408-to-2604).

## Before you begin

Create a full backup of the vtenext instance and record the current Exchange configuration. Check at least:

- current connector version;
- Exchange type in use;
- enabled synchronization modules;
- users using the connector;
- folders selected by users;
- custom mappings for Contacts and Organizations;
- any existing synchronization errors.

## Why the registration script is required

The script registers the existing Exchange Connector as a vtenext vtlib module. It does not reinstall the connector and must be run **only once** on an instance coming from the 20.04.xx family.

The full operational procedure is described in [Migrating from 20.04.xx to 24.08 or 26.04](https://manual.vtenext.ch/books/exchange-connector-vtenext-Hfx/page/migrating-from-2004xx-to-2408-or-2604).

## If Microsoft 365 is used

The new generation uses Microsoft Graph for Exchange Online. Before migration, decide whether to use the **vtenext Proxy** or a **Custom Microsoft App**. Differences, requirements and configuration are described in [Configuring Microsoft 365](https://manual.vtenext.ch/books/exchange-connector-vtenext-Hfx/page/configuring-microsoft-365).

## If Exchange Server is used

For on-premises Exchange Server, the module structure still has to be migrated, while communication continues to use EWS. See [Configuring Exchange Server](https://manual.vtenext.ch/books/exchange-connector-vtenext-Hfx/page/configuring-exchange-server).