E-Mail sending to Offcie/Microsoft365 customers not possible - 451 4.7.500 Server busy

Koes 360

Hi,

since this morning 5 am we are not able to send E-mails to office365/Microsoft365 Customers. Our Mails are stuck in our own queue and get the response: host customername.mail.protection.outlook.com 451 4.7.500 Server busy please try again later wit 193.228.149.133 S77719

Can someone check, why we are on an throtteling list with our E-MailServer and remove please?

Koes 360 Reputation points

2023-10-11T10:47:21.94+00:00

Problem seems to be known to Microsoft Exchange Online Team,

Title: Some users may encounter delays receiving external email messages in Exchange Online User impact: Users may encounter delays receiving external email messages in Exchange Online. More info: Affected users may see a "451 4.7.500 Server busy" error message. Current status: We’ve identified that specific IP addresses are being unexpectedly limited by our anti-spam procedures, causing inbound external email delivery to become throttled and delayed. We're reviewing if there have been any recent changes to our anti-spam rules to understand why the IP addresses are being limited. In the meantime, we're manually adding reported affected IP addresses to an allowed list to provide immediate relief. Scope of impact: Impact is specific to some users who are served through the affected infrastructure. Next update by: Wednesday, October 11, 2023 at 2:30 PM GMT+2
Alexander Shvedko 50 Reputation points

2023-10-11T11:07:38.01+00:00

Is there a form in Microsoft where you can send a request and your IP addresses so that they can be added to the exception?
Didier BIBAL 10 Reputation points

2023-10-11T11:21:39.45+00:00

We v got the same issue since this morning
Dror Katz 10 Reputation points

2023-10-11T11:30:16.3733333+00:00

Hi, any good news, we also have the problem from today.
Gillis Dirk 20 Reputation points

2023-10-11T11:40:55.75+00:00

We have the problem in Belgium but not in Germany.
04449962 5 Reputation points

2023-10-11T11:55:43.46+00:00

Update 16:06 GMT +2
Answer to my ticket:

Please note we have run a backend diagnostic related to the issue, and it will take some time to come into effect. So, we would request to kindly check and confirm the behavior.

---------------------------------------------------------------------------------------------

We're experiencing the same issue in Greece. I opened a support ticket this morning, but there's no solution yet. Changing our server's IP allows us to send emails to Exchange Online temporarily. We're informing our customers that this problem is not on our end but rather with Microsoft.
Freddie Leeman 5 Reputation points

2023-10-11T11:56:10.9733333+00:00

The same issue is occurring in the Netherlands. The email queue is reaching 1500 messages, causing a significant backlog. :(
TN Krishnamurthy 0 Reputation points

2023-10-11T12:02:14.49+00:00

We are facing the same problem,. Our Server also receives the message wither "Server Busy" or "Too many recipients" Can any one give the details of the form for informing our IP address and requesting them to add
Perger Balázs 5 Reputation points

2023-10-11T12:08:18.6966667+00:00

We have the same problem in Hungary. Does anyone know where I can request IP removal? Thx!
Staff Ancara 0 Reputation points

2023-10-11T12:11:59.8633333+00:00

Hello, same issue here, Italy. We obtain "Server Busy" or "Too many recipients" sending to Microsoft mailservers.Also changing sending IP address with an already warmed IP address not solve the issue.
Ajay Rooplall 15 Reputation points

2023-10-11T12:14:53.0966667+00:00

We are also having this issue in South Africa.
Peter Ny 5 Reputation points

2023-10-11T12:17:32.7666667+00:00

Does anyone know where I can request IP removal?
If it is blacklisting... But if not? Does anyone know anything about this?
Administrateur IAF (Fournisseur) 1 Reputation point

2023-10-11T12:22:34.3833333+00:00

We have the same problem here in France. Our 5 servers with different IPs are affected.
Mathieu Morier 0 Reputation points

2023-10-11T12:55:23.6933333+00:00

We have the problem in Canada ( EAST Region )
Nefise Uçar [Erdemir] 0 Reputation points

2023-10-11T13:08:43.5766667+00:00

We're experiencing the same issue in Turkiye.
Perger Balázs 5 Reputation points

2023-10-11T13:17:57.72+00:00

@outlook.com
Please allow IP address 62.100.224.108

Thank you!
Anonymous

2023-10-11T13:21:04.8433333+00:00

In Poland we have the same problem

Please add to Whitelist

194.213.1.14

194.213.1.29
Koes 360 Reputation points

2023-10-11T13:21:48.19+00:00

actually, i think, noone from exchange online team is reading here :(
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Alexander Shvedko 50 Reputation points

2023-10-11T13:23:07.3566667+00:00

Please add to whitlelist:-

unma.unistaff.com

37.230.155.10
Bilal Ümit 0 Reputation points

2023-10-11T13:26:31.8866667+00:00

Same problem in Turkey/Türkiye

212.252.192.101
Bassam Shahtoot 0 Reputation points

2023-10-11T13:31:21.5866667+00:00

Hi, I have a problem also in this IP:
212.29.201.108
Anonymous

2023-10-11T13:46:33.4+00:00

Hello dear Supportteam,

our IP is also affected:

[IP removed from comment]

Edit: it is now the next morning and the problem seems to be resolved
SALAZAR Joaquim 0 Reputation points

2023-10-11T13:48:40.5933333+00:00

Same problem in Switzerland.
Any light about a possible solution?
WBS Blank Software 0 Reputation points

2023-10-11T13:50:55.5133333+00:00

In the meantime, we're manually adding reported affected IP addresses to an allowed list to provide immediate relief.

@outlook.com , please allow this affected IP to your whitelist:

80.154.9.145
Thanks
Jeff Straley 0 Reputation points

2023-10-11T13:59:51.2833333+00:00

PLEASE ADD OUR PUBLIC IP: 216.68.72.94
Pedro Valmor 0 Reputation points

2023-10-11T14:01:21.8166667+00:00

We are facing the same issue in Brazil.
Craig 0 Reputation points

2023-10-11T14:05:06.8166667+00:00

Same here in Ontario. Can I get our Company Whitelisted Please.

721.14.166.196
Alexandre Chaves Fonceca 0 Reputation points

2023-10-11T14:19:30.1333333+00:00

Hi,

we have the same problem, hundreds of emails in queue already, in 187.103.208.3 and 187.49.32.4 servers...

please, whitelist them!
Houssem 0 Reputation points

2023-10-11T14:27:51.3733333+00:00

Hi

We are facing the same Errors in Tunisia

@outlook.com , please allow these affected IPs to your whitelist:

196.224.96.6

196.224.96.4

197.26.11.132

197.26.11.133
Wojciech Kunda 0 Reputation points

2023-10-11T14:38:26.07+00:00

Problem since morning observed in Poland. No reaction on ticket (https://olcsupport.office.com/).

Could anyone whitelist 195.242.92.0/24, please?
Kevin Lynch 0 Reputation points

2023-10-11T14:44:20.11+00:00

Please whitelist 168.245.66.188
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Alain D 21 Reputation points

2023-10-11T14:47:48.3766667+00:00

@MS : Do you have an estimation time for resolution ?
Ledl.net GmbH 0 Reputation points

2023-10-11T14:48:00.05+00:00

Same issue for Austria and various IP-addresses (senders):

213.145.228.64
213.145.225.20
213.145.225.90
213.145.224.230
213.145.224.150
Radu Minoiu 0 Reputation points

2023-10-11T14:50:23.63+00:00

Please add IP 93.115.7.133 (Romania, Bucharest) - E-Novator Data SRL, mail.enovator.ro
Mattias Forss 0 Reputation points

2023-10-11T14:59:43.5966667+00:00

Incident EX680695
Some users may encounter delays receiving external email messages in Exchange Online
Affected services: Exchange Online
https://admin.microsoft.com/Adminportal/Home#/servicehealth/:/alerts/EX680695
IT Support Netwizard 0 Reputation points

2023-10-11T15:01:54.7666667+00:00

@Microsoft support @Outlook please whitelist 201.20.145.214, 201.20.145.231, 201.20.145.207, 201.20.145.210.

Thank you
國書葉 0 Reputation points

2023-10-11T15:05:38.4066667+00:00

Same problem in Taiwan,

Name: spamsqr.gce.com.tw

Address: 59.124.137.84
Sherif AboulGadayel 0 Reputation points

2023-10-11T18:55:16.2266667+00:00

It looks solved now. All emails in the server queue are relayed to domains hosted at outlook.com
Kai Yao 37,791 Reputation points Moderator

2023-10-12T02:20:23.68+00:00

Hi @All,

This issue should have been fixed.

Please have a check if mail flow is now working for you.

And due to security concern, please edit or hide your ip addresses in the post since this is a public forum.
PDC COMPUTER 0 Reputation points

2023-10-13T10:05:49.6933333+00:00

We in Vietnam and Thailand are similarly affected
Andres Gavino 0 Reputation points

2023-10-28T00:21:36.22+00:00

Hello, we own a small landscaping company in California and we are being affected please allow

75.142.221.255
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Rajmond Kovács 0 Reputation points

2023-11-15T12:25:25.77+00:00

Hungary is also affected.

Please whitelist:

mail.t-online.hu

84.2.46.11

195.228.240.65

Thank you in advanced.
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Hurajp 0 Reputation points

2024-05-01T17:03:17.1266667+00:00

hello broo..
Araibet Login 0 Reputation points

2024-06-13T11:16:58.24+00:00
Is this happening all over the world or is it only a few countries experiencing it?

From what I read, some countries don't experience the same thing

Araibet Login
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Bhus Hanetai 0 Reputation points

2024-07-22T02:43:42.88+00:00

Perhaps this is a sync error
LEEBILLY 0 Reputation points

2024-09-13T10:27:45.1366667+00:00

We have the problem in Hong Kong today, Pls fix it asap. tks
gary bertrand 0 Reputation points

2024-10-05T16:21:30.39+00:00

Can anyone help with password Frequency on MSN Authenticator
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
IT-Glocke 0 Reputation points

2025-02-28T12:03:46.3233333+00:00

Hello, please whitelist 93.188.24.252. We have the same issue. Thank you
IT-Glocke 0 Reputation points

2025-02-28T12:13:22.8033333+00:00

Hello, please whitelist 93.188.24.252. We have the same issue. Thank you

175 answers

SEKHAR KAMTI 0 Reputation points

2025-03-27T15:55:30.3933333+00:00

Hello, the same for exchange server IPs 115.113.181.45 and 125.18.124.174 from India.
Was this answer helpful?
SEKHAR KAMTI 0 Reputation points

2025-03-27T18:10:32+00:00

Hello,

I am adding the remaining Exchange server IPs where we are experiencing issues.

115.113.181.46

220.227.52.45

220.227.52.46
Sign in to comment

Use comments to ask for clarification, additional information, or improvements to the question.
Rahul Bag 0 Reputation points

2025-09-19T13:19:28.6666667+00:00

Hello, the same for exchange server IPs 115.113.181.45, 220.227.52.45 and 125.18.124.174 from India.
Was this answer helpful?

0 comments No comments
Sign in to comment

Use comments to ask for clarification, additional information, or improvements to the question.
Ahmet Ercömert 0 Reputation points

2025-10-02T12:10:56.1166667+00:00

Hello, please whitelist 88.255.128.4 We have the same issue in Turkey. Thank you
Was this answer helpful?

0 comments No comments
Sign in to comment

Use comments to ask for clarification, additional information, or improvements to the question.
Allen Li 0 Reputation points

2025-10-09T02:29:30.5733333+00:00

Hello, please whitelist 21vianet Exchange Online.

From IP 218.250.140.179

To IP 52.101.132.28

We have the same issue in China and Hong Kong. Thank you
Was this answer helpful?

0 comments No comments
Sign in to comment

Use comments to ask for clarification, additional information, or improvements to the question.
Namespro 0 Reputation points

2026-01-22T22:23:29.35+00:00
Hi,

Please help us whitelist the following IPs:

38.15.146.216/29

209.127.13.246/32

169.54.78.252/30

Thanks!
- Kelvin from Canada
Was this answer helpful?

0 comments No comments
Sign in to comment

Use comments to ask for clarification, additional information, or improvements to the question.

E-Mail sending to Offcie/Microsoft365 customers not possible - 451 4.7.500 Server busy

175 answers

Your answer