As of 9:17 AM EST / 2:17 PM UTC, Nov 13, 2026 (Microsoft's latest update we confirmed): Microsoft says service availability is still improving, with email queues significantly reduced and approaching normal levels. Some users may still see intermittent access issues or delayed email delivery, and the incident has not been marked resolved. We update this post only when something meaningful changes.
You click Send, and nothing happens. You end up with Outlook stuck in Outbox, a bounce-back error, or a message saying Outlook is disconnected. Before you restart your laptop for the third time, it's worth asking one question: is the problem on your side, or Microsoft's?
Outlook not sending emails almost always comes down to one of those two. Whether Outlook can't send email for a single message or for every message, this guide helps you tell which in a few minutes, then walks you through the fix that matches.
Quick answer: Open Outlook on the web (outlook.office.com) and check the Microsoft 365 status page. If sending fails there too, or Microsoft lists an Exchange Online problem, it's Microsoft's issue and no local fix will help. If the web works and only your desktop app fails, it's your setup. Jump to the fixes below.
Today's situation: Microsoft's admin center lists incidents EX1550543 and MO1550821 for this disruption. If you're seeing Outlook not sending emails today, follow our live post, Microsoft 365 Outage Today: Live Status and Workarounds, before trying any fixes. Multiple teams have reported sending failures on Outlook desktop and mobile.
What Microsoft has confirmed
Microsoft says users may be unable to connect to multiple Microsoft 365 services. Features that depend on Exchange Online are affected: Outlook mailbox access can fail on the web, desktop and Exchange ActiveSync, and email delivery may be delayed. Teams calendar scheduling, invites and live events also fail, while calls, meetings and chat mostly work.
Microsoft has said it is not aware of malicious activity. A Post-Incident Report will follow, and we'll describe the cause exactly as Microsoft states it.
Step 1: Is Outlook Not Sending Emails Because of Microsoft?
If Microsoft reports a problem with Exchange Online, the service that runs your Microsoft 365 mailbox, nothing on your computer will fix it. These checks take about two minutes.
Open the Microsoft 365 status page. If it lists a problem with Exchange Online or Outlook, the issue is on Microsoft's side. Microsoft also posts updates on @MSFT365Status.
Ask your IT admin to check Service health. In the Microsoft 365 admin center, Health > Service health lists incidents for your organisation, such as today's EX1550543 and MO1550821. If the admin center won't load, Microsoft points admins to the public status page above.
Ask a colleague to send an email. If Outlook can't send email for them either, the problem is unlikely to be your own setup.
Try Outlook on the web or the mobile app on cellular data. If sending fails everywhere, it points to the service rather than your computer.
If these checks point to a Microsoft problem, stop troubleshooting.
Leave unsent messages in your Outbox. They usually send once service recovers.
Don't resend the same email repeatedly. Recipients may get duplicates when the queue clears.
Don't reinstall Office or rebuild your profile. It won't help during a service incident.
Use another channel for anything urgent. A phone call, SMS or Teams call or chat works for most people. Don't send sensitive data over personal email.
Watch for phishing. Attackers exploit big outages with fake "fix" emails. Go straight to Microsoft's status page instead.
Step 2: Match Your Symptom
If Microsoft reports no problems, find your symptom below. It usually shows why you're seeing Outlook not sending emails and which fix to try.
| What you see | Points to | What to do |
|---|---|---|
| Outlook won't open your mailbox on web, desktop or phone, and colleagues see the same | Microsoft | Follow the status page; no local fix needed |
| "Disconnected" or "Working Offline" in Outlook's status bar | Your setup | Turn off Work Offline (fix 1) |
| Outlook stuck in Outbox on one email while others send | That message | Check its attachment size (fix 2) |
| A bounce-back message with a code like 5.1.1 or 5.2.2 | The recipient or the address | Read the code (fix 3) |
| A warning that your mailbox is full | Your mailbox | Free up space (fix 4) |
| Sending stops after a large batch of emails | A sending limit | Check limits (fix 5) |
| Outlook can't send email on the desktop app, but Outlook on the web sends fine | Your desktop Outlook | Sign in again, try safe mode and a profile repair (fixes 6, 7 and 8) |
Step 3: Outlook Can't Send Email and Microsoft Is Healthy? Try These Fixes
Work through these in order, starting with the quickest. The menu names below are for classic Outlook for Windows; new Outlook and Outlook for Mac use similar options in different places.
Turn off Work Offline. On the Send / Receive tab, click Work Offline so it is no longer highlighted. Outlook should reconnect and send what's waiting.
Outlook stuck in Outbox? Check for large attachments. Outlook stuck in Outbox is commonly caused by a message that's too large. Exchange Online's default limit is 35 MB per message, and your admin may have set a lower one. Open the stuck message, remove the attachment, and share it as a OneDrive link instead, then send again.
Read the bounce-back code. A 5.1.1 code usually means the recipient's address doesn't exist, 5.2.2 means their mailbox is full, and 5.7.x codes mean the message was refused for permission or policy reasons. Codes starting with 4 are temporary, so the server will usually retry.
Free up mailbox space. Once a mailbox reaches its quota, Exchange Online stops it from sending. Empty Deleted Items, archive old mail, or ask your admin about your quota.
Check you haven't hit a sending limit. Exchange Online allows up to 10,000 recipients per user in a rolling 24 hours, 30 messages per minute, and 500 recipients per message by default. The daily limit counts recipients, not messages. If you send in bulk, split the send or ask your admin. See Microsoft's Exchange Online limits.
Sign in again. An expired password or changed MFA setting can quietly stop sending. Sign out of Outlook and sign back in, and if a password prompt keeps looping, clear the stored entry in Windows Credential Manager.
Start Outlook in safe mode. Close Outlook, press Windows + R, type outlook.exe /safe and press Enter. If sending works there, an add-in is the likely problem; disable add-ins one at a time to find it.
Repair your Outlook profile (classic Outlook). Go to File > Account Settings > Account Settings, select your account and choose Repair.
If Outlook not sending emails continues after all eight fixes and Microsoft still reports no issues, contact your IT team with the exact error text and the time it happened.
For IT admins
Open Microsoft 365 admin center > Health > Service health and look up EX1550543 (Exchange Online mailbox access) and MO1550821 (wider Microsoft 365 impact).
Use message trace in the Exchange admin center to see whether messages are queued, delayed or failing.
If only one user can't send, check whether the account has been restricted in the Microsoft Defender portal.
Send staff a short notice on what is and isn't affected, so your helpdesk isn't flooded with duplicate tickets.
When the email comes from your business systems
Not every business email is sent by a person. Your ERP or automation tools may send invoices, purchase approvals and order confirmations automatically, and many send them through your Microsoft 365 mailbox. If those emails stop going out, check Microsoft's status first. If Microsoft reports no problems, the cause is usually in that system's own email settings.
If you would like help finding out why your system stopped sending, talk to a Versich consultant. You can explore our full range of services, read about our NetSuite Support Services, try the NetSuite Free 30-Minute Fix for a single quick issue, or see how n8n workflow automation can alert you when business emails stop.
