Email delivery delays

Summary

This guide helps you troubleshoot and resolve: Email delivery delays. Follow the steps below to fix the issue.

Common Causes

Overview

Emails taking too long to arrive? This guide helps diagnose and fix email delivery delays in Microsoft 365.

Normal Delivery Times

• Internal emails: Usually instant (seconds to 1–2 minutes)
• External emails: Typically 1–5 minutes
• High‑volume periods: May take longer during business hours

Warning signs: Emails taking 15+ minutes consistently.

Quick Checks

1. Check Your Send/Receive

1. In Outlook, click the Send/Receive tab.
2. Select Send All to force delivery.
3. Verify that no messages are stuck in the Outbox.

2. Check the Outbox for Stuck Emails

1. Open the Outbox folder.
2. If messages are present, double‑click each one and click Send, or resolve any error messages.

3. Verify Your Internet Connection

• Open a web page to confirm connectivity.
• If the connection is slow, email delivery may be delayed.

4. Review Attachment Size

Microsoft 365 allows attachments up to 150 MB (configurable up to 150 MB). Larger files should be shared via OneDrive and sent as a link.

5. Check Service Health

Visit the Microsoft 365 Service health dashboard for any known mail‑flow incidents that could affect delivery.

Troubleshooting Steps

Force Account Sync

1. Click Send/Receive → Update Folder in Outlook, or press F9.

Repair Outlook Account

1. Go to File → Account Settings → Account Settings.
2. Select your email account and click Repair.
3. Follow the wizard to complete the repair.

Clear Outlook Cache

1. Close Outlook completely.
2. Press Win + R, type %localappdata%\Microsoft\Outlook\RoamCache and press Enter.
3. Delete all files in this folder.
4. Reopen Outlook.

Check Quarantine and Spam Filters

Inspect Transport Rules

Use Message Trace

1. Open the Microsoft 365 Admin Centre and navigate to Exchange admin centre → Mail flow → Message trace.
2. Filter by date, sender, and recipient to locate delayed messages.
3. Examine the trace details for any “Queued” or “Deferred” status.

PowerShell Queue Inspection (Admins)

Connect-ExchangeOnline -UserPrincipalName admin@yourdomain.com
Get-Queue | Where-Object {$_.MessageCount -gt 0} | Format-Table Identity,MessageCount,NextHopDomain
Get-MessageTrace -Recipient "user@domain.com" -StartDate (Get-Date).AddDays(-1)

Check Email Queue (For IT/Admins)

1. Sign in to the Microsoft 365 Admin Centre.
2. Open the Exchange admin centre.
3. Navigate to Mail flow → Message trace and search for messages that are queued or delayed.
4. Review any transport rules or connector issues that may be causing bottlenecks.

Prevent Future Delays

• Avoid sending large attachments during peak Microsoft service periods.
• Keep attachment sizes under 150 MB or use OneDrive links.
• Maintain a stable internet connection.
• Regularly update Outlook and apply Microsoft 365 updates.
• Consider using Outlook on the web as a backup during outages.

Still Having Issues?