Recent Discussions
OAB download fails after hybrid mailbox move.
Hi folks, I'm posting this query here as I doubt anyone in the Outlook forums would have the necessary Exchange hybrid knowledge. I run a classic hybrid Exchange environment where Exchange Server 2019 CU15 is the on-premise platform. Authentication is provided by on-premise AD FS, with the accounts being synchronised from on-premise via AAD Connect. I've just moved my on-premise mailbox to Exchange Online via New-MoveRequest and for the most part, everything is fine. One thing that possibly isn't fine - going off the Bits-Client event log is the regular offline address book downloads, where I'm seeing regular failures in the event log and through double-checking with bitsadmin.exe. The initial address book synchronisation worked as the view in Outlook is fully populated, however, I expect that future changes likely won't come through. bitsadmin output Event log output (There's numerous events to choose from - this is the one I'm most curious about.) The BITS service provided job credentials in response to the UNIDENTIFIED authentication challenge from the outlook.office365.com server for the Microsoft Outlook Offline Address Book <guid> transfer job that is associated with the following URL: /OAB/<guid>/oab.xml. The credentials for the <sid> user were rejected. When the mailbox was on-premise, the OAB came from the Exchange Server - no surprise there, where post migration it can be seen from the bitsadmin output it now comes from outlook.office365.com. Perhaps that's also to be expected - I don't know, but it makes sense given the move. What alerted me to there potentially being an issue is the systray icon frequently gets stuck on the "synchronising" icon, and running a manual full OAB sync from within Outlook fails to complete. After an extended "hang" period, the sync window eventually times out with the error shown above (the protracted UI behaviour would appear to be due to the large number of retries). Dropping the BITS job URL into Edge simply returns a HTTP 503, which doesn't necessarily strike me as a problem. After all, I'm unable to provide a BEARER token using this method. I haven't yet tried via PowerShell as it only occurred to me now but perhaps I'll do so after posting this. Searching on this error and scenario has turned up nothing useful. I have also checked and compared event log entries from an Azure AD-native account, where it's a mixed bag of successful OAB BITS downloads and unsuccessful ones that feature the same symptoms as above, which offers up the possibility this might be a transient service-side error (though I'm not leaning heavily towards this). Has anyone else encountered this issue and resolved it? Is it even an issue to begin with, or is this expected behaviour? I'm unsure what to make of the symptoms. Cheers, Lain
Proper whitelisting of microsoft.com on dnswl.org
I keep having the issue that system-generated e-mails, e.g. on Trace Reports get classified as spam by the receiving e-mail provider. The sender address is email address removed for privacy reasons and the e-mails go to my M365 mailbox and are redirected to my external monitoring mailbox with that e-mail provider. The e-mail provider calculates a score that includes checking the sender's IP address 52.101.69.91 with dnswl.org . Unfortunately, that address is only whitelisted for outlook.com and some secondary domains, but not for microsoft.com. Of course, the issue also occurs with mailto:email address removed for privacy reasons and other IP addresses, so this is an example. It started to occur around two weeks ago, not sure if the provider changed policies or Microsoft changed the whitelisting; of course the provider refuses to overrun dnswl.org it, e.g. by own whitelisting. Who at Microsoft could I ask to fix that kind of issues? I don't find any appropriate category in their support menues, M365 support says the cannot help (TrackingID#2603031420001611). Thanks in advance for any hints, this is my first posting here, so please forgive me, if this is a dumb question.
Could any one explain Exchange Server SE Licensing Model?
I have the following M365 licenses in my education tenant: Microsoft 365 A5 without Audio Conferencing (Student Use Benefit) As per my understanding, each user requires an A3/A5 license to access their mailbox on an Exchange Server (Exchange SE). Since A3/A5 licenses already include Exchange Online, do we still need to assign these licenses to each on-premises user, or is this only for compliance purposes? For example, if we have 100 on-premises users, must all 100 users be assigned A3/A5 licenses in Microsoft 365? Reference articles are below. Microsoft Product Terms Please correct me if I am wrong.
Recent Blogs
- We wanted to provide a reminder that Exchange 2016 and 2019 ESU program ends in October 2026.Jul 20, 2026
- We have released Security Updates for Exchange Server SE. Exchange Server 2019 and 2016 ESU updates only.Jul 14, 2026
