MS Mail servers claim Hotmail domain does not exist
In my Gmail account I have a rule that forwards everything to my Hotmail/Outlook account where I primarily read all of my mail. This has worked well for a long time until the 16th January 2026 when I started to realise I was missing a few mails. Looking in the Gmail inbox I could see a few NDRs from Googlemail saying that it had failed to forward a message. I'm assuming this is an issue at the Microsoft end as the NDRs say it is a remote (i.e. Microsoft) mail server claiming that the domain Hotmail.co.uk doesn't exist, so the mail gets bounced. BTW, this is not an issue with my individual account, my wife and I have similar setups (both our Gmails forward to our Hotmails) and we both started having the same issue from that date. The key NDR details are always of this form: Address not found Your message wasn't delivered to ***@hotmail.co.uk because the domain hotmail.co.uk couldn't be found. Check for typos or unnecessary spaces and try again. The response from the remote server was: 501 5.5.4 Invalid domain name [AM4PEPF00027A67.eurprd04.prod.outlook.com 2026-01-20T22:06:56.421Z 08DE543D7B61AE38] So, it looks like some server in the chain is claiming that the whole domain "hotmail.co.uk" cannot be found!!! Surely I can't be the only one with this issue? I guess many people will be unaware they're missing mails as the original senders will be the ones receiving the NDRs, and where that is a company (rather than an individual) they probably just bin them and never investigate. This seemed to get worse over a few days and then stabilise to ~25% of mails failing: 16th Jan - 3 of 31 emails had this issue 17th Jan - 0 of 19 failed 18th Jan - 3 of 16 emails had this issue 19th Jan - 1 of 34 emails had this issue 20th Jan - 5 of 27 emails had this issue 21st Jan - 10 of 34 emails had this issue 22nd Jan - 8 of 31 emails had this issue 23rd Jan - 8 of 28 emails had this issue The issue seems to be random, there is no pattern with the times of day or senders - sometimes a particular sender is fine (e.g. Netflix, eBay), sometimes they suffer this issue. In the NDRs I'm not sure what the naming convention of the Outlook servers is but re. the above example's "AM4PEPF00027A67.eurprd04.prod.outlook.com", I've looked at all the servers mentioned in each NDR (up to 22nd) and again there's no real pattern - the hostname's always begin with either AMS0, AMS1, AM3, AM4, DB1, DB3, DB5, DU2, DU6, with the 4 character ones being followed by "EPF000xxxxx" and the 3 character ones being followed by "PEPF000xxxxx". The following subdomain is always eurprd02-eurprd05 with just two examples using EURPRD83. I did try and report to Outlook.com but their online help system currently gives an error (Error 500.30 - ASP.NET Core app failed to start). I hope this is a better place where someone might have a chance of convincing someone that there is a mail server config error somewhere?
Setting up mail forwarding of an account with no Outlook license
Hi, Currently we have an account that can be used to log into office.com. There's no Outlook license applied to the account. As a result, if someone sends an email to it, it will be sent back because it's not a valid email address. (e.g. due to not having a license, there's no mailbox). I was wondering if it's possible to setup mail forwarding on this account? Or would it require an Outlook license? Sincerely, Jason
Email sent from Shared Mailbox gets stuck in Outbox
Hello, I am working with a client who has a primary and shared mailbox in Outlook. They are using the newest version of classic Outlook desktop app and they have full permissions to the shared mailbox, including "send as" permissions. They can send email from their primary mailbox without issue. However, when they send email as the shared mailbox, it gets stuck in the Outbox and never sends. I have tried the following: 1. Removing the profiles re-adding 2. Deleting the Outlook data files 3. Reducing cache to as low as 3 months 4. Turning off cache but when I do the shared mailbox gets an error that it cannot connect to the Exchange server 5. Turning on auto-archive to shrink the data files 6. Switching to "New Outlook". This does seem to work but the company uses a plug-in for a program called "Mail Manager" and they don't fully support New Outlook yet Sometimes these solutions will fix the issue for a few days to a week but then it begins happening again. This issue does not happen when they are using the mobile or web clients. To me this sounds like a corrupted data file but I can't pinpoint what exactly is causing the corruption. Any suggestions? Thanks, Mike
Synchronization issue in New Outlook for Mac – ״Failed to refresh subscriptions.״
Hello, I am using Microsoft 365 (Exchange Online) on Mac, running macOS 26.1 (Tahoe). My Outlook client is: Outlook for Mac Version 16.103.3 (25113013), with a Microsoft 365 Subscription license. Since yesterday morning, in the New Outlook interface, my inbox has suddenly appeared empty, and I constantly receive the following error message: “Failed to refresh subscriptions.” It’s important to note: In Legacy Outlook, everything works perfectly. The web version and the Outlook app on my mobile phone also work well. The issue persists regardless of the network I am on (home, office, cellular, etc.). Troubleshooting steps I already tried: • Updating Outlook to the latest version • Removing and re‑adding the account • Clearing cache and preferences • Formatting my Mac and reinstalling everything from scratch Unfortunately, none of these steps has resolved the issue. Is this a known bug, and is there a recommended workaround or an upcoming fix? Appreciate assistance on that issue.Outlook broke after Office 365 update to 16.0.19328.20158 – cannot open emails Windows Server 2016
Hello everyone, posting to report that after the latest automatic update to Microsoft Office 365 version 16.0.19328.20158, we are experiencing a critical issue on multiple company machines running Windows Server 2016: The Outlook desktop application launches normally, but when trying to open any email, the following error appears: “There was a problem opening this item... The text formatting command is not available... Reinstall Microsoft Outlook.” Launching Outlook in safe mode (Outlook /safe) does not help. Creating the FORMS2 folder (suggested workaround) does not fix it. Attempting a downgrade via OfficeC2RClient.exe fails with error 30183-27 (400). Quick/online repair from Control Panel also has no effect. In our environment, this issue appeared simultaneously on many workstations and servers, right after the Office update today. Temporary solution: We are instructing users to access their mail via Outlook Web App (OWA), which is not affected by this bug. We would like to know: If others have experienced this bug with this build, including on Windows Server 2016 If any working workaround exists, or an official fix timeframe from Microsoft Thanks to anyone who can share their experience or updates!
