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How do you make a Shared Mailbox the default Send From account? (New Outlook)
I'm using Outlook for Windows version 1.2025.109.100 (on behalf of another user). I'm reading some suggestions online that say you need to add the account to Outlook first before making it the default Send From. I'm also looking at the Help section in Outlook that directs you to change this in the Compose and Reply settings. However, it's not possible to sign into a mailbox that isn't a user. I thought you used to be able to 'sign into' a shared mailbox using your own account but that is not the case now (perhaps it never was?). What it seems like is that we instead need to convert "Accounting" to a User account, give it a license, then sign into it in Outlook. That's not a Shared Mailbox - that's a user mailbox. I don't want to create a point of weakness for a potential cyber-attack (which we've had several). I can't really set up MFA for this account that no one can maintain. And I really don't want to have to spend money on a license to do something just because one piece of software is incompatible. Having to repeatedly instruct people and then repeatedly remind them to change their FROM account is just bonkers. On Outlook for Mac, as long as you're in the Shared Mailbox, the default FROM is that mailbox. (but, don't get me started on how much better the Mac version of Outlook is than the Windows version - see: All Accounts)
Exchange SMTP Auth Fails with: 451 4.7.0 Temporary server error. Please try again later. PRX5
Office 365 refuses SMTP authentication with error: 451 4.7.0 Temporary server error. Please try again later. PRX5 This is when accessing External Send SMTP AUTH through OAUTH2 authentication. Initial authentication is successful (and is logged as so in Entra ID) but when trying to send send messages through authenticated SMTP, you get the above error. Working with multiple support reps, we looked through login logs and could not find any trace of the error in Entra ID. Support reps all blame the third party application. The issue is connected to a special use case, where a user has both the GLOBAL ADMIN role, as well as certain other admin roles. When you have a certain combination of those roles, for a selected user, OAUTH2 will fail, even though OAUTH2 for (apparently) ALL OTHER SERVICES - work without error! - ONLY SMTP Auth is affected. RESOLUTION: Keeping Global Admin while simply removing excess roles will almost immediately resolve the issue. This bug has been publicly noted as far back as August 2022, perhaps earlier. This needs to be fixed.
OOF to personal emails dropped at EOP relay
Issue: When an OutOfOffice recipient is gmail.com, outlook.com, msn.com ,etc, relay is dropped by EOP. Oof is delivered when recipient is an M365 tenant. Any other mail flows no issues to gmail and other personal addresses as well. It's only OOF to personal addresses. Env: Exch 2016 with EOP send/receive (hybrid manually, not hcw) We found 2 blog posts might be relevant, but these instructions did not resolve: https://techcommunity.microsoft.com/blog/Exchange/updated-requirements-for-smtp-relay-through-exchange-online/3851357 https://techcommunity.microsoft.com/blog/exchange/enhanced-filtering-for-connectors---improving-deliverability-and-minimizing-fals/4160483 This is what we see on the smtp protocol log: >,MAIL FROM:<> SIZE=7072, >,RCPT TO:<****@gmail.com> NOTIFY=NEVER, <,250 2.1.0 Sender OK, <,550 5.7.64 TenantAttribution; Relay Access Denied [*****.eurprd03.prod.outlook.com 2025-01-04T14:03:21.934Z *****], >,QUIT, ### We also looked into dkim, but finally found this line: By design, Exchange Online Protection uses the high risk delivery pool (HRDP) to send OOF replies, because OOF replies are lower-priority messages. https://learn.microsoft.com/en-us/exchange/troubleshoot/email-delivery/understand-troubleshoot-oof-replies#what-are-out-of-office-replies We feel this is not likely a connector or ceritifcate or onprem issue, rather something with HRDP and OOF in EOP. Could you confirm we are on the right track now? If not the Exchange Team can help please let me know who. Thanks
Move request falsely stuck
We are migrating mailboxes cross forest between two Exchange organizations and are having an issue with 3 of them. We were migrating these 3 mailboxes when the target Exchange server had the log disk filling-up, and move request seemed to be stuck. We extended the disk and the move actually completed, we check the get-moverequest for "non completed" and none was reported. We move the mailbox database, on the target DAG, between the two hosts and then, not sure if it's related, the get-moverequest reported three entries in "waitingforjobpickup" even if the migrationa has successfully completed, the mailbox is active on the destination and users are connecting without issue. How can we clear the status correctly or we just can delete the move request ? thanks SC
Exchange Online courses
Hello all, Since Microsoft ended the MS-203 certification and courses, there is no training available anymore. On the Micorosft Learn website there aren't courses about Exchange 365; only the 'manage complaince in Exchange 365'. Does any of you know if there will be a new training for Exchange 365 soon? Where do you find courses for Exchange 365 (and Defender for Office/Exchange). Kind regards, Arjan
Unable to change mailbox permissions
Hi, We have inherited a Hybrid Exchange environment. It consists of 1 on-prem Exchange Server (Version 15.0 (Build 1473.3)) and M365. All the mailboxes have been migrated to M365 and ADSync is present to replicate to M365. The issue we have is that even as a Global and Exchange admin in M365, we are unable to edit the permissions of any users mailbox. Doing this via the M365 admin centre just returns a message saying "Something Went Wrong." If we try it in Powershell we get a "User is not allowed to call" message. We are trying to understand if this is an issue with M365 or we are trying to make the permission change from the wrong location? In a hybrid environment where all mailboxes have been migrated, from where you should you make permission changes to a mailbox? Is there something else we are doing wrong here? Thanks DBMS Exchange SE 2025
Recently, I came to know that MS will next Exchange in Subscription Edition (https://techcommunity.microsoft.com/discussions/exchange_general/exchange-server-subscription-edition-arrives-in-summer-2025/4133577). The MS exchange 2025 will be the update of 2016 and 2019 version and 2016 and 2019 support will be the end of 2025. My query is new MS Exchange 2025 SE will be on-prem or cloud-based. If it is cloud-based, then the Active Director will be cloud-based, too. Can anyone clarify me those things.
