Mail flow delays in Exchange Online impacting message delivery

Question

Mail flow delays in Exchange Online impacting message delivery

Davila Bobby 60

I’m experiencing a critical issue in Exchange Online where outbound and internal emails are being delayed for 30–60 minutes before delivery. Message Trace shows status “Pending” for a long time, even for internal recipients. No transport rules were recently changed, and connectors look normal.

Nicolas Bourdeau - Wintive 135 Reputation points

2025-11-06T10:26:09.78+00:00
Hi Davila,

That kind of delay is definitely abnormal — especially if internal mail is also affected and nothing has changed in terms of transport rules or connectors.

Here are a few things to check immediately:

🔎 1. Service Health Dashboard (SHD)

Log into https://admin.microsoft.com > Health > Service Health, and look for any Exchange Online incidents (e.g. EX####). Microsoft occasionally has backend issues that cause mail queues to hang even if your own config is fine.

📊 2. Queue Viewer (via PowerShell)

Check the queues:

Get-Queue | ft Identity,Status,MessageCount,NextHopDomain

If queues are large and stuck in "Retry" or "Pending," it often means a backend delivery issue or spam filter delay.

🧪 3. Advanced Message Trace (Defender Portal)

You can dig deeper here: https://security.microsoft.com > Email & collaboration > Email trace Look for delays at the Transport or Filtering level (anti-spam/anti-malware).

Let me know if this is a hybrid setup or pure cloud — that can change the behavior as well.

— Nicolas Bourdeau | Link removed by Moderator. Do not replace

Microsoft 365 Consultant – Exchange | Teams | SharePoint

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Nicolas Bourdeau - Wintive 135 Reputation points

2025-11-06T10:26:09.78+00:00

Hi Davila,

That kind of delay is definitely abnormal — especially if internal mail is also affected and nothing has changed in terms of transport rules or connectors.

Here are a few things to check immediately:

🔎 1. Service Health Dashboard (SHD)

Log into https://admin.microsoft.com > Health > Service Health, and look for any Exchange Online incidents (e.g. EX####). Microsoft occasionally has backend issues that cause mail queues to hang even if your own config is fine.

📊 2. Queue Viewer (via PowerShell)

Check the queues:

Get-Queue | ft Identity,Status,MessageCount,NextHopDomain

If queues are large and stuck in "Retry" or "Pending," it often means a backend delivery issue or spam filter delay.

🧪 3. Advanced Message Trace (Defender Portal)

You can dig deeper here: https://security.microsoft.com > Email & collaboration > Email trace Look for delays at the Transport or Filtering level (anti-spam/anti-malware).

Let me know if this is a hybrid setup or pure cloud — that can change the behavior as well.

— Nicolas Bourdeau | Link removed by Moderator. Do not replace

Microsoft 365 Consultant – Exchange | Teams | SharePoint

Answer 1

Hi @DavilaBobby,

Welcome to Microsoft Q&A, and thank you for reaching out to us.

Based on your descriptions, could you confirm whether this issue started recently or has been ongoing for some time? Does it occur when sending bulk emails or individual messages?

Additionally, is the problem happening across all Outlook platforms (Classic, New, and Web) or only on one specific platform?

In the meantime, please ensure that your DNS and authentication records (SPF, DKIM, and DMARC) are correctly configured. Receiving servers often perform these checks before accepting mail and missing or incorrect configurations can make your emails appear suspicious, which may lead to additional scanning or quarantining and slow down delivery.

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You can also check the headers on delayed emails. Look at the “Received” header chain in the affected messages from both the sender and recipient mailboxes. This will help you pinpoint where the delay occurred and whether the message was held up in Microsoft’s transport system.For more information on how to check message header, feel free to check on this Microsoft Article here.

Additionally, I recommend creating a support ticket in the Microsoft 365 Admin Center. As a forum moderator, I can share general guidance on common Exchange Online issues, but I don’t have access to your tenant configuration or logs. My suggestions are therefore based on publicly available information and best practices. Kindly note to gather as much detailed information as possible when reaching to Microsoft Support Team, as this will help ensure the most effective troubleshooting.

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I hope the guidance I’ve shared helps address your concerns. If you have any questions or need further clarification, please don’t hesitate to let me know. I’m happy to assist you further.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

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Mail flow delays in Exchange Online impacting message delivery

🔎 1. Service Health Dashboard (SHD)

📊 2. Queue Viewer (via PowerShell)

🧪 3. Advanced Message Trace (Defender Portal)

0 additional answers

Your answer