[German]Microsoft has released the 2023 H1 Cumulative Update for Exchange Server 2019, effective May 3. Also sailing under the acronym CU13, the update brings Modern Auth to Exchange 2019 and Outlook on Windows and is said to fix nearly 200 bugs. Microsoft says the setup preserves the administrator's custom configuration settings.
I became aware of this release via subsequent tweet from Scott Schnoll, senior product marketing manager for Exchange Online and Exchange Server and for Microsoft 365 Networking. Microsoft announced it in the Techcommunity post Released: 2023 H1 Cumulative Update for Exchange Server.
The tweet lists the support status (including CU minimum requirements) in a table. The newly announced CU13 includes fixes for customer-reported issues, according to Microsoft, along with all previously released security updates (SUs), including updates in the March 2023 SU. A full list of fixes is included in KB article KB502099 for the CU (I haven't found a KB article yet). The download is available at the VLSC and here, according to the Technet article (but a German reader notes, that installing the update didn't change anything – only old files are installed – possibly the official fresh release won't come until Patchday, on May 9, 2023). At the same time, CU13 also brings two new features.
Modern authentication
The update introduces the support for OAuth 2.0-based authentication (referred to by Microsoft as Modern auth) for on-premises Exchange Server 2019 installations. Currently, it is limited to Modern auth support for Outlook on Windows in Exchange Server 2019, with support for other Outlook clients (Mac OS, Android and iOS) expected later this year. Outlook on the Web and ECP already support request-based authentication with ADFS, which is a form of modern authentication.
Backup and restore configuration
A common issue for many customers is that CU's overwrite various configuration files (for example, web.config and sharedweb.config) that contain custom settings, such as custom message size limits. After installing a CU, these customizations are usually lost, and the administrator must reapply them. For this reason, administrators often back up and restore their custom settings or use scripts to recreate custom settings after installing a CU.
To address this issue, Setup now backs up the most common configuration settings and then restores them to the state they were in before Setup was started. Starting with the CU 2023 H1, Setup keeps about 70 different configuration settings in multiple files. For more information about this feature, see Exchange Server User Configuration Backup.
