Why does outlook.com refuse to deliver my emails

Peter Fox2 20 Reputation points
2026-03-16T04:53:32.6733333+00:00

I have an outlook.com email account. The email client on my PC is Outlook Classic (365 subscription).

I compose an email with 31 addressees and send. It immediately bounces as 'undeliverable'.

Why?

I understand that 31 addressees is well within the limit set. Am I wrong?

 

Diagnostic information for administrators:

 

Error is [0x80004005-0x00000b22-0x00000501].

 

Exchange response headers:

      request-id: [Moderator note: PII removed]

      X-ServerApplication: Exchange/15.20.9700.017

      X-FEServer: ME3P282CA0059

      X-CalculatedBETarget: SE1P216MB2581.KORP216.PROD.OUTLOOK.COM

      X-RequestId: {[Moderator note: PII removed]}:59

      X-ClientInfo: {[Moderator note: PII removed]}:217000017

      X-ElapsedTime: 1462

      X-BackEndHttpStatus: 200

      X-ResponseCode: 0

      X-RequestType: Execute

 

ROPs Summary:

 

      0: ropSetProps (10) Processed(1) Completed(0)

            ROP result: 0

            Response codes: 0

      1: ropSetProps (10) Processed(1) Completed(0)

            ROP result: 0

            Response codes: 0

      2: ropSetProps (10) Processed(1) Completed(0)

            ROP result: 0

            Response codes: 0

      3: ropFlushRecipients (14) Processed(1) Completed(0)

            ROP result: 0

            Response codes: 0

      4: ropSetProps (10) Processed(1) Completed(0)

            ROP result: 0

            Response codes: 0

      5: ropTransportSend (74) Processed(1) Completed(0)

            ROP result: 0

            Response codes: 2850

 

Response Exceptions:

 

ROP Index: 5

ROP Associated: ropTransportSend (74)

Microsoft.Exchange.Data.Storage.OutboundSpamException: WASCL UserAction verdict is not None. Actual verdict is RefuseQuota.

   at Microsoft.Exchange.Data.Wascl.WasclHelper.PerformAntiSpamCheck(IStoreSession session, ICoreItem coreItem, Func`1 activityScopeGetter)

   at Microsoft.Exchange.Data.Wascl.WasclHelper.PerformAntiSpamCheck(IStoreSession session, ICoreItem coreItem)

   at Microsoft.Exchange.Data.Storage.Adapters.ObjectEventHandlers.WasclEventsHandler.Handle(BeforeItemSendEvent beforeItemSendEvent)

   at Microsoft.Exchange.Data.StoreObjects.EventHandler.EventDispatcher.ExecuteHandler[TEvent]

   at Microsoft.Exchange.Data.StoreObjects.EventHandler.EventDispatcher.Dispatch[TEvent]

   at Microsoft.Exchange.Data.Storage.CoreItem.PreprocessItem(String apiName)

   at Microsoft.Exchange.Data.Storage.CoreItem.TransportSend(StorePropertyDefinition[]& properties, Object[]& values)

   at Microsoft.Exchange.Data.StoreObjects.ProxyCoreItem.TransportSend(StorePropertyDefinition[]& properties, Object[]& values)

   at Microsoft.Exchange.Data.Storage.Items.CloudCacheSendProxyCoreItemDecorator.TransportSend(StorePropertyDefinition[]& properties, Object[]& values)

   at Microsoft.Exchange.RpcClientAccess.Handler.Message.TransportSend()

   at Microsoft.Exchange.RpcClientAccess.Handler.RopHandler.<>c__DisplayClass156_0.<TransportSend>b__0()

   at Microsoft.Exchange.RpcClientAccess.Handler.ExceptionTranslator.TryExecuteCatchAndTranslateExceptions[TResult]

 

 

Transport-Send failed: failure enum(25), HResult(0x00000000), EC(2850).

Transport-Send failed: failure enum(22), HResult(0x00000000), EC(2850).

Submit-Message failed: message id(1), failure enum(13), HResult(0x80004005), EC(2850).

Outlook | Web | Outlook.com | Email
0 comments
Answer accepted by question author
Kal-D 7,375 Reputation points Microsoft External Staff Moderator
2026-03-16T16:55:03.2+00:00

Please note that our Microsoft Q&A forum is a public platform, and we will modify your response/ question to hide your personal information in the description. Kindly ensure that you hide any personal or organizational information the next time you post an error or other details to protect personal data.  

Hi Peter Fox2,

Based on the diagnostic you posted, this isn’t the “maximum recipients per message” limit.

The key line is: Microsoft.Exchange.Data.Storage.OutboundSpamException … Actual verdict is RefuseQuota

That means Outlook.com refused the send due to outbound anti‑spam / quota enforcement. Even if you have a Microsoft 365 subscription and are using Outlook Classic, an @outlook.com / @hotmail.com mailbox is still a consumer Outlook.com service, and it remains subject to consumer sending limits and spam heuristics (these are separate from Exchange Online / business tenant limits).

  • Hitting daily recipient limits
  • Sending to many non‑relationship recipients (people you haven’t emailed before)
  • Bulk‑like patterns, especially heavy Bcc usage

What to try next:

  • Test from Outlook on the web (Outlook.com) by sending a small message to 1–2 recipients.
    • If it fails on the web as well > this confirms an account‑level quota/heuristics block. Send in smaller batches (for example, 5–10 recipients at a time), minimize Bcc use, and retry after the quota window clears.
    • If it works on the web > the issue is client‑side. You can then test Outlook Classic in Safe Mode (outlook.exe /safe), recreate the message, or create a new Outlook profile.

If you recently sent a high volume of messages or recipients, you may need to wait for the sending quota to reset. This often clears within about a day, but the exact timing depends on account reputation and usage history.

For reference: Sending limits in Outlook.com.

If you can confirm whether the send also fails on the web, and whether most recipients were new or added via Bcc, that will help narrow it down further.

Please let me know if this proves useful to you, or if you would like further assistance.

I'm looking forward to your reply.

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  1. Peter Fox2 20 Reputation points
    2026-03-17T08:32:28.7733333+00:00

    Thank you for your help.

    This was the first attempt to 'bulk' email, 31 addressees - members of my tennis club, NO BCC.

    Previous emails from that outlook.com email address have been to fewer than 6 addresses, NO BCC.

    The highest number of emails sent in any week over the last three months is 8, most weeks fewer than 3, so I shouldn't have hit any limits or sending quotas.

    I resent the email in batches of 10 and that worked, just inconvenient.

    I guess it is what it is. next time I will try (say) batches of 16 - if that works it will be more convenient.

    Again, thanks for your help, have a good one.

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