440 Login Timeout - OWA (Exchange 2019)

Question

i hve case in exchange 2019 cu15,
When a user logs in to OWA, it works fine - but when user clicks on Reply or Forward to any email, the user gets kicked out and OWA asks user to login again.

i get log from browser inspect mention Status code 440

Has anyone experienced something similar?

Answer 1

Hi @Imam Prayitno

Thank you for posting your question in the Microsoft Q&A forum.  

To better assist you, could you please provide additional information on the following: 

Is the issue affecting all users or only specific individuals? 

Have there been any recent changes in your Exchange environment (e.g., updates, configuration modifications, or security patches)? 

I also found some relevant discussions that may help. You can refer via: 

Users Unable to Access Webmail or Outlook After Upgrading Exchange 2019 to CU15 - Microsoft Q&A 

Exchange 2019 OWA kicking out - Software & Applications - Spiceworks Community 

Note: Microsoft is providing this information as a convenience to you. These sites are not controlled by Microsoft, and Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please ensure that you fully understand the risks before using any suggestions from the above link. 

Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution. 

---

Note: Please follow the steps in [our documentation] to enable e-mail notifications if you want to receive the related email notification for this thread. 

Answer 2

The described behavior (user can sign in to OWA but is forced to re‑authenticate when replying/forwarding) is typically caused by issues with OWA authentication cookies or modern browser security changes, and in Exchange 2019 these are addressed in later cumulative updates.

For Exchange Server 2019 CU15 specifically, install the latest available cumulative update for Exchange 2019. Several OWA sign‑in and post‑sign‑in issues (including authentication loops and cookie handling problems) are fixed only in newer CUs:

1. If using ADFS/Hybrid/Modern Auth and browsers with reduced referrer headers, an authentication loop can occur because OWA does not set all required cookies. This is fixed starting with Exchange 2019 Cumulative Update 5 and later. Updating to a current CU ensures the corrected behavior for the referrer header and OWA cookies.
2. If SSL offloading is used and clients are on modern Chrome/Edge, OWA can appear to work until certain actions (such as opening or replying to messages) when cookies marked SameSite=None but not Secure are rejected by the browser, causing re‑authentication or blank pages. This is fixed starting with Exchange 2019 Cumulative Update 11 and later.
3. In coexistence topologies with Exchange 2016 and extended protection enabled, OWA logon failures after credential entry are resolved in Exchange 2019 Cumulative Update 13 and later.

Because CU15 predates these fixes, upgrade the Exchange 2019 servers to the latest cumulative update and then retest OWA reply/forward. Ensure all Client Access servers behind any load balancer are updated to the same CU so that authentication cookies and sessions are handled consistently.

If a load balancer is in use and not all servers can be updated immediately, configure persistence (source‑IP stickiness) so that a user’s OWA session remains on the same server until the environment is fully updated.

---

References:

• Authentication loop between msft.sts.microsoft.com/adfs and OWA in Exchange Server 2019 and 2016
• Can't log on to OWA in Chrome if SSL is offloaded in Exchange Server 2019 and 2016 (KB5006993)
• OWA stops responding in an Exchange 2019 and 2016 coexistence topology
• Cannot log in to OWA or ECP after July 2021 SU for Exchange Server 2019, 2016, and 2013 (KB 5005341)