Exchange Server 2019: No more CUs in 2023; CU14 and CU15 coming in 2024

Exchange Logo[German]Brief information for administrators of Microsoft Exchange Servers who are waiting for the cumulative update for the second half of 2023. Redmond has announced that two outstanding cumulative updates (CUs) for Exchange Server 2019 will no longer be rolled out in 2023, but will be postponed to 2024. This is because no more CUs will be rolled out in December 2023. For example, TLS 1.3 support has been announced with CU14.


Two CUs per year in March and September

Microsoft had already announced in 2022 that the maintenance model for Exchange Server would be adjusted so that only two cumulative updates (CUs) would be rolled out per year. These CUs will preferably be released in the first and second half of each calendar year, with Microsoft aiming to release them in March and September.

However, Microsoft also emphasizes that these release dates of March and September are not set in stone. Release dates for CUs are based on various constraints. Microsoft gives as examples "the payload and quality" of the CU, which can lead to delays in the release of CUs. Translated, this means: "If we change a lot, it can take longer to finish. And if we mess up during implementation and happen to notice it before release, it can also take longer until a release is due." It is also possible that other work, such as the publication of a security update (SU), can delay a CU release.

The CUs will not arrive until 2024

Microsoft released the 2023 H1 Cumulative Update for Exchange Server 2019 on May 3, 2023 (see Exchange Server 2019: 2023 H1 Cumulative Update released (May 3, 2023)). The update, which also is abbreviated as CU13, brought the Modern Auth implementation for Exchange 2019. So far, I was not aware of any other CU for Exchange Server 2019 (would then be the 2023 H2 Cumulative Update, or CU14, in Microsoft nomenclature). A list of the CUs can be viewed here.The next regular patch day would be December 12, 2023, so not that long away. Microsoft could then deliver cumulative updates (CUs) for Exchange Server 2019 that are already in development and planned. In the following tweet, I came across the fact that Microsoft wants to delay the rollout.

Exchange 2019 CUs

In the Techcommunity article Servicing Exchange Server 2019, the Exchange team talked about the rollout of the planned CUs for Exchange Server 2019 on November 21, 2023. So far, they have not managed to roll out the cumulative update 2023 H2 for Exchange Server 2019, and now there are less than two weeks left in November 2023. In December 2023, Microsoft did not roll out any more CUs for Exchange Server due to the holidays.


The release date of CU14 has been postponed from 2023 to early 2024 for the reasons mentioned above. CU14 is now likely to be released after January 9, 2024. Microsoft promises many benefits for CU14, including support for TLS 1.3, a fix to S/MIME control, enhanced protection enabled by default and more.

Attention: Mainstream support ends

In its Techcommunity post, the Exchange Server team points out the lifecycle scheme for Exchange Server 2019. This reaches the end of mainstream support on January 9, 2024, i.e. there should actually (as I understand it so far) be no more functional changes to the product. General support for Exchange Server 2019 will then end on October 14, 2025 – I am not yet aware of a successor. Microsoft does not want to introduce this until 2025 (Software Express has some information here, and in the Techcommunity article there is a suggestion in the comments that Microsoft will announce something at the beginning of 2024).

Exchange Server 2016 ist bereits am 1. Oktober 2020 aus dem Mainstream-Support gefallen, und der Support endet ebenfalls am 14. Oktober 2025.

However, Microsoft is now announcing a special feature: CU14 will most likely be released after January 9, 2024, i.e. after the end of mainstream support. With the planned CU15, Microsoft will even release two cumulative updates after the end of mainstream support in 2024. This could confuse some customers.

But Microsoft also solves this mystery with an explanation from the Exchange Server team. Although January 9, 2024 is the end of mainstream support for Exchange 2019, it is not the deadline for the release of CUs. January 9, 2024 is the last date for Microsoft to allow customers to request a bug fix or Design Change Request (DCR) for the Exchange team to consider. The team will accept requests for bug fixes and DCRs until January 9. After this date, Microsoft's developers will only consider security fixes.

If I translate this again: Microsoft's Exchange Server team has received so many requests for bug fixes and Design Change Requests (DCR) that they have split this into two CUs (CU14 and CU15). CU14 was actually supposed to be released in H2 2023 and CU15 in H1 2024, but because Christmas is just around the corner, as it is every year, H2 2023 will be released as H1 2024, which means that CU15 and H1 2024 will be postponed to H2 2024.

In 2025, the cards will be reshuffled with the successor to Exchange Server 2019. As the Microsoft team writes "In this case, we will release not just one, but two CUs after the end of mainstream support. We are simply delivering on our customer promises." Within the comments, a Microsoft employee wrote, that an announcement for Exchange vNext will probably given in Spring 2024.

Cookies helps to fund this blog: Cookie settings

This entry was posted in Software, Windows and tagged . Bookmark the permalink.

3 Responses to Exchange Server 2019: No more CUs in 2023; CU14 and CU15 coming in 2024

  1. srfndoc says:

    How do they expect companies to move to with 2019 general support ending on 10/25? That give people less than a year for migrations… for large companies with clusters across the globe this will be impossible. The only way I see this working is if "" comes as a CU and allows you to upgrade cluster nodes in place.

    Fun times…

Leave a Reply

Your email address will not be published. Required fields are marked *