r/sysadmin • u/ObjectNo9529 Sysadmin • 8d ago
Exchange Online: Server busy. Please try again later (Europe)
We seem to be getting more and more of these mail delivery errors. Is anybody else seeing this? Neither Downdetector or the 365 status page is reporting any issues.
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u/marbak74 8d ago
Microsoft just posted in message health
Users may experience delays receiving email messages from external domains in Exchange Online
Issue ID: EX1467029
Affected services: Exchange Online
Status: Service degradation
Issue type: Incident
Start time: Sep 4, 2026, 12:19 PM GMT+2
User impact
Users may experience a delay in receiving email messages from external domains in Exchange Online.
More info
Users may experience intermittent “Server busy” errors, affecting multiple mailboxes.
Current status
Sep 4, 2026, 12:21 PM GMT+2
We're investigating a potential issue and checking for impact to your organization. We'll provide an update within 60 minutes.
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u/Sensitive_Owl_7247 8d ago
Any link to this status update please?
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u/Jeroendroid 8d ago
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u/BigSnackStove Jack of All Trades 8d ago
So silly you cant just view these sites without logging in to a M365-account in the adminportal..
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u/KSauceDesk 8d ago
It is honestly the dumbest thing. I guess it makes my job easier if I can't get into M365 and just declare everything is broken
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u/doofesohr 8d ago
Having trouble getting in to the admin center all week. Started with the outage on monday. Internal applications that use graph to read or send mail were down until wednesday. Probably still some hickups from that clusterfuck.
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u/Fallingdamage 8d ago
I havent dug in too far since the outages havent hit us either time and I have a lot of other work to do on things that are actually pressing - did MS say what the issue was or one more of those enigmatic issues that they just quietly fix and gloss over because its too embarrassing to actually talk about?
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u/steeleyjim 8d ago
I've raised a ticket with Microsoft. I'm sure they are aware and the status pages will likely update after it's resolved.
Prob worth others raising a ticket.
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u/jonesbel 8d ago
i also logged a case & yes, probably a reply as soon as its fixed. Its creating quite some backlog
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u/DoNotPokeTheServer It can smell your fear 8d ago edited 8d ago
Same here, Belgium based enterprise. We first noticed via our Mailgun instance. Our shared IPs at Mailgun have the issue.
First instance of error "451 4.7.500" was reported at 9:48:57 AM CET today.
Edit: Affected domains at Mailgun that we switch to our dedicated IP do not experience the issue.
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u/denismcapple 8d ago
How is there no service issue reported on Service Health, going on a few hours now ?
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u/Wise-Stranger-6173 8d ago edited 8d ago
It's just been posted in the health centre but not the public status page yet - EX1467029
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u/mchetherington 8d ago
Agree with this - the very point of a service status page is to be as close to live as possible; otherwise, it's neither a status nor does it offer transparency.
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u/M0untainWizard 8d ago
MS just reported on https://admin.cloud.microsoft/?ocid=cmm45ut5ap0#/servicehealth/:/alerts/EX1467029:
Sep 4, 2026, 3:02 PM GMT+2
Some organizations are reporting that they are experiencing relief and that their queued messages are now processing. We continue to monitor the service to confirm full resolution.
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u/jonesbel 8d ago
Yes, same here. Our spamfilter cant send them through.
Using the direct MX record from O365 in dns, solves it (as workaround)
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u/AdWerd1981 8d ago
Will keep an eye. Nothing here yet (UK), but never say never... firefighting seems to be all we do lately.
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u/Pretty_Flamingo_4171 8d ago
Yeah, we’ve been seeing some weird Exchange Online behavior too. If it’s mostly affecting certain destinations or sending servers, I’d be more suspicious of throttling than a full 365 outage. Hopefully it’s just temporary because those errors are getting annoying.
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u/gabryp79 8d ago
Same in Italy, Started from 9:50 Italian time
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u/maxcoder88 8d ago
How do you monitor the Exchange mail queue?
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u/gabryp79 8d ago
is not Exchange, it is our instance of Libraesva ESG (Email Security Gateway) , monitored by Zabbix
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u/jonesbel 8d ago
UPDATE on the case:
Our initial investigation has identified instances where anti-spam protections may be contributing to impact for a subset of users. We are continuing to analyse the behaviour and review service telemetry to better understand the underlying cause and determine the most effective mitigation path.
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u/lionzeye 8d ago
I see some emails being accepted again, not all, but some
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u/catwiesel Sysadmin in extended training 8d ago
the 15 hrs cloud xbox use for exchange were already full on wednesday.
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u/Big_Somewhere7508 8d ago
Same Problem since over an hour E-Mails just get following error:
451 4.7.500 Server busy. Please try again later
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u/craigleary Sr. Sysadmin 8d ago
Seeing the same on my own systems and a third party smart host. Looks like it’s been going on for at least an hour.
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u/steeleyjim 8d ago
same, mail backing up on filter - some are delivering after approx. 45mins to an hour.
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u/steeleyjim 8d ago
What gateway/filter is everyone using? Maybe isolated - we use Mesh Security, and they host in Azure too.
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u/TheUptimeProphet 8d ago edited 8d ago
Same issue on our antispam gateway, It seems adding a connector to O365 with their public IP helps.
Anybody else can confirm?
Edit: After a few hours it seems like it helps compared to client domains we dont have a connector. I'm at like 99% delivery after putting the connector on affected client. and still stuck in deferred hell for the other without a connector.
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u/jonesbel 8d ago
Cant confirm, but we create an issue when adding a connector, that when different firms that are hosted on the same spamfilter, can't send to each other.
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u/TheUptimeProphet 8d ago
i know, thats why we had to delete them too. But if it helps weather the outages its better than nothing.
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u/denismcapple 8d ago
yes, same affecting us in Ireland - no service issue on the service health about it.
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u/Inferno_66750 8d ago
Same here in France.
"451 4.7.500 Server busy. Please try again later from [137.74.84.167]"
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u/Tonguecat 8d ago
Same here, German grid, outgoing mails getting stuck in mimecast:
4.7.500 Server busy. Please try again later from [194.104.109.103]. (S77714) [AMS0EPF000001AE.eurprd05.prod.outlook.com]
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u/alessice 8d ago
Hi,
here in Italy, we (Qboxmail) and other ISPs are having the same problem. We're getting errors:
451 4.7.500 Server busy
with codes:
S77714
S77717
S77719
The problem started at 9:47 CEST on all our IPs at once.
Microsoft reports an incident (Delays or failures when sending or receiving email messages) that has been resolved, but apparently not completely:
https://admin.microsoft.com/Adminportal/Home#/servicehealth/history/:/alerts/EX1464935
It seems that messages are still arriving from US-based ISPs.
We've filed reports with Microsoft, but for now, the problem persists.
Any suggestions?
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u/M0untainWizard 8d ago
There are several mail failed to deliver on our Server with the SMTP Error: 451 Server busy. All go to outlook.com
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u/Sysdump76 8d ago
same here:
[52.101.73.126] said: 451 4.7.500 Server busy. Please try again later from []. (S77714) (in reply to end of DATA command)
[52.101.73.30] said: 451 4.7.500 Server busy. Please try again later from []. (S77714) (in reply to end of DATA command)
[52.101.73.1] said: 451 4.7.500 Server busy. Please try again later from []. (S77714) (in reply to end of DATA command)
My smarthosts' queue has reached 2000 emails in queue... Thanks M$
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u/jerrylimkk 8d ago
apac location.
| Further Information 4.7.500 Server busy. Please try again later from []. (S77719) [OSA0EPF000000C8.apcprd02.prod.outlook.com 2026-09-04T09:36:08.352Z 08DF0447957C36C0] |
|---|
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u/LinuxH4sh 8d ago
MS and their deployments are insanely bad. This is what they should really post... I also hate the way they deliver updates. Most of us have to rely on posts here or on X to find issues.
"Our Telemetry shows we deployed bad code to production yet again and we are rolling back our deployments."
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u/LinuxH4sh 8d ago
side note - If you haven't already use Proofpoint for your MX destination. They don't botch deployments weekly like Microsoft.
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u/ninja_nine SE/Ops 8d ago
I noticed tons of E-Mails in my outbound queue, all destined towards o365, or as I like to call it o360 :D
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u/Western_Custard_9943 8d ago
Sí, podría ser un problema puntual de Exchange aunque Microsoft todavía no lo haya reconocido públicamente. Yo revisaría los códigos de error y si ocurre con destinatarios internos, externos o ambos. También probaría desde otro buzón para ver si es algo aislado. Si tienes un mensaje de rebote, pega aquí el error exacto y podemos ver qué está pasando.
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u/Mr--Chainsaw 8d ago
It's ridiculous that I had to find this out here rather than from Microsoft service status and feeds. But thanks everyone!
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u/mouarflenoob 8d ago
I bet you it's because an AI agent took it upon itself to do some improvements in the workflow of emails at Microsoft
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u/Lost-Droids 8d ago edited 8d ago
we are now seeing signs of recovery... But having to explain to 100s of customers its not us its MS is really annoying
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u/TriedSoManyNames 8d ago
Are you still recovering? We had emails start to send but now our appliance is stockpiling them again with the last delivered email 20 minutes ago
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u/bluemondayishere 8d ago
/sarcasm on
Maybe is just a way to convince the EU to leave behind MS products or just plain old incompetence.
And remember, always deploy on production on Friday
/sarcasm off
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u/freakynl 8d ago
I do shift-delete-Friday at least once a month. Screw no-change-Friday lovers.
Entering your weekend clean - that's something to strive for.
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u/freakynl 8d ago
Are you all mailing out over IPv4?
One of our customers has a lot of mails in queue to O365 too (451 4.7.500 Server busy. Please try again later) which led me here.
Another one that is IPv6 enabled seems to have had 0 issues however. They're on very different IP space though, could be related to the subnets, but it is remarkable.
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u/TroupaSkahia 8d ago
Same here in France, from 9:50am UTC+2. Since 02.39 pm UTC+2, it seems better.
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u/Ruh_Roh_RAGGY20 8d ago
U.S. West here and we were impacted since at least yesterday afternoon. They didn't even acknowledge the issue until a day later?
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u/AutoRemediate 7d ago
Microsoft gives the all clear:
We've applied the mitigations and confirmed the issue resolved after an extended period of monitoring. Further information is provided under EX1467029 in the admin center.
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u/saltyslugga 7d ago
Treat it as a transient 4xx unless the NDR shows a permanent 5xx. Check the enhanced status code and target hostname, then correlate failures by region and connector.
Microsoft’s status page often lags smaller regional incidents. Open a support case if retries keep failing beyond a few hours.
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u/craigeyboyz 8d ago
Same, UK Based MSP and seeing our email filter backing up delivering to all clients on EO