Outlook not sending emails is one of the most frustrating issues you can run into, especially when you have something urgent to deliver. The good news is that most of the time, the fix is simple. This guide walks you through every real solution, from quick checks to deeper troubleshooting, so you can get back to sending emails fast.
Why Outlook Stops Sending Emails
Before jumping into fixes, it helps to understand what usually causes this problem. Outlook fails to send emails for a few common reasons:
- Your email is stuck in the Outbox folder
- Outlook is working in offline mode
- Your SMTP server settings are wrong
- Your internet connection dropped or is unstable
- An Outlook add-in is interfering
- Your Outlook profile is corrupted
- Antivirus or firewall software is blocking the connection
- Your email account password changed recently
- The email has a large attachment that exceeds the server limit
Knowing the cause helps you pick the right fix. Start from the top of this list and work your way down.
Fix 1: Check If Outlook Is in Offline Mode
This is the most common reason Outlook stops sending emails and the easiest fix.
How to check:
- Open Outlook
- Click the Send/Receive tab at the top
- Look for the Work Offline button
- If it looks highlighted or pressed, click it to go back online
Once you disable offline mode, Outlook will reconnect and try to send any emails sitting in your Outbox automatically.
Fix 2: Check the Outbox Folder
If an email gets stuck in the Outbox, it blocks everything else from going out. This happens more often than people realize.
Steps to fix a stuck Outbox:
- Go to your Outbox folder in the left sidebar
- If you see emails sitting there, open one
- If it opens in read-only mode, close it first
- Right-click the stuck email and choose Delete if you do not need it
- If you do need it, move it to Drafts, edit it, and resend
Sometimes the stuck email has an oversized attachment. Check the file size. Most email servers reject attachments over 25 MB.
Fix 3: Check Your Internet Connection
Outlook needs a live internet connection to send emails. If your connection is slow or dropped, emails will not go out.
Quick checks:
- Open a browser and load any website
- If it loads slowly or not at all, restart your router
- Try switching from Wi-Fi to a wired connection if possible
- After reconnecting, go to Send/Receive in Outlook and press F9 to manually trigger a send
Fix 4: Fix Your SMTP Server Settings
Wrong outgoing server settings will stop Outlook from sending every time. This is especially common after switching email providers or setting up a new account.
How to check your SMTP settings:
- Go to File > Account Settings > Account Settings
- Select your email account and click Change
- Click More Settings then go to the Outgoing Server tab
- Make sure My outgoing server (SMTP) requires authentication is checked
- Go to the Advanced tab and verify the SMTP port
Common SMTP port settings:
| Email Provider | SMTP Server | Port | Encryption |
|---|---|---|---|
| Gmail | smtp.gmail.com | 587 | TLS |
| Outlook/Hotmail | smtp.office365.com | 587 | TLS |
| Yahoo Mail | smtp.mail.yahoo.com | 465 | SSL |
| Custom/cPanel | mail.yourdomain.com | 587 | TLS |
If any of these are wrong, correct them and click OK. Then try sending again.
Fix 5: Re-enter Your Email Password
If you recently changed your email account password and forgot to update it in Outlook, every send attempt will fail silently.
How to update your password:
- Go to File > Account Settings > Account Settings
- Click on your account then click Change
- Update the password field with your new password
- Click Next and then Finish
Outlook will now use the correct credentials when connecting to your mail server.
Fix 6: Repair Your Outlook Account Profile
A corrupted Outlook profile can cause all kinds of problems, including emails not sending. Repairing it is straightforward.
Steps:
- Open Outlook and go to File > Account Settings > Account Settings
- Select your email account
- Click Repair
- Follow the on-screen prompts
- Restart Outlook after the repair is done
If repair does not fix the issue, try creating a brand new Outlook profile:
- Close Outlook
- Open Control Panel and search for Mail
- Click Show Profiles
- Click Add and create a new profile
- Set it up with your email account
- Open Outlook using the new profile and test
Fix 7: Disable Add-ins That Are Causing Conflicts
Third-party add-ins can interfere with how Outlook sends mail. Antivirus plugins, CRM integrations, and email tracking tools are common culprits.
How to disable add-ins:
- Open Outlook and go to File > Options > Add-ins
- At the bottom, next to Manage, select COM Add-ins and click Go
- Uncheck all add-ins
- Restart Outlook and try sending an email
If email sends successfully, re-enable add-ins one by one to find which one is causing the issue.
Fix 8: Start Outlook in Safe Mode
Safe mode starts Outlook without any add-ins or customizations. It is a great way to isolate whether the problem is with Outlook itself or something added to it.
How to open Outlook in Safe Mode:
- Press Windows + R on your keyboard
- Type
outlook.exe /safeand press Enter - Try sending a test email
If it works in safe mode but not normally, an add-in is the problem. Go back to Fix 7 and disable them.
Fix 9: Check Your Antivirus and Firewall Settings
Antivirus software sometimes scans outgoing emails and accidentally blocks them. Firewalls can also block the port Outlook uses to connect to the SMTP server.
What to do:
- Temporarily disable your antivirus and try sending an email
- If it works, add Outlook as an exception in your antivirus settings
- Check your Windows Firewall and make sure Outlook is allowed through
- If you are on a corporate network, contact your IT team since firewalls are often managed at the network level
Fix 10: Update Outlook to the Latest Version
An outdated version of Outlook can have bugs that prevent emails from sending. Updates also include security patches that help Outlook connect reliably to mail servers.
How to update:
- Open Outlook
- Go to File > Office Account
- Click Update Options > Update Now
- Let the update install and restart Outlook
If you are using Microsoft 365, updates usually happen automatically, but checking manually does not hurt.
Fix 11: Repair the Office Installation
If nothing above has worked, the Outlook installation itself may be corrupted. Running a repair fixes missing or damaged files.
Steps for Windows:
- Open Control Panel > Programs > Programs and Features
- Find Microsoft Office in the list
- Right-click and choose Change
- Select Quick Repair first and click Repair
- If Quick Repair does not work, repeat the steps and choose Online Repair
Online Repair downloads fresh files from Microsoft and is more thorough. It takes longer but fixes deep corruption issues.
Fix 12: Check Email Size Limits
Every email server has a maximum size limit for outgoing emails. If your email has large attachments, it will fail to send without a clear error message in many cases.
General size limits:
| Provider | Max Email Size |
|---|---|
| Gmail | 25 MB |
| Outlook.com | 20 MB |
| Office 365 | 25 MB (configurable by admin) |
| Yahoo Mail | 25 MB |
If your attachment is too large, use a cloud storage link instead. Upload the file to OneDrive, Google Drive, or Dropbox and share the link in your email. This is a better practice regardless, since large attachments often get blocked by recipients’ servers too.
Fix 13: Check for Server-Side Issues
Sometimes the problem is not on your end at all. The email server itself could be down or experiencing issues.
How to check:
- For Microsoft 365 or Outlook.com, check the Microsoft Service Status page for any active incidents
- For Gmail accounts configured in Outlook, check Google’s status dashboard
- For custom email hosting, contact your hosting provider
If there is an active server outage, there is nothing to do except wait for it to be resolved.
Fix 14: Test with a New Email Message
Sometimes a specific email is the problem, not Outlook itself. A broken email with unusual formatting or encoding can fail to send.
Test this quickly:
- Create a brand new email
- Keep it simple: one line of plain text, no attachments, no formatting
- Send it to yourself
- If it goes through, the original email had a problem
If the test email sends fine, start a fresh version of your original email and rebuild it.
When to Contact Microsoft Support
If you have tried everything above and Outlook still will not send emails, it is time to contact support. This is especially true if you are on a corporate Microsoft 365 plan, where IT admins may need to check server-side configurations, send quotas, or account-level blocks.
For personal accounts, Microsoft’s support chat is available directly from the Outlook app under File > Help > Contact Support.
Outlook Not Sending Emails on Mobile
If the problem is on the Outlook mobile app rather than desktop, the fixes are slightly different.
For iOS and Android:
- Go to your phone’s Settings > Accounts and remove the Outlook account
- Re-add the account from scratch
- Make sure the Outlook app is updated to the latest version
- Check that your phone has a live internet or mobile data connection
- Toggle airplane mode on and off to force a reconnection
Conclusion
Outlook not sending emails is almost always fixable without expert help. The most common culprits are offline mode, stuck Outbox emails, wrong SMTP settings, or a conflicting add-in. Start with the simple checks, work your way through the deeper fixes only if needed, and you will have it sorted quickly. Keep Outlook updated, use cloud storage for large files, and check server status before assuming the problem is on your end. That alone will save you a lot of troubleshooting time in the future.
Frequently Asked Questions
Why are my Outlook emails stuck in the Outbox and not sending?
Emails get stuck in the Outbox when Outlook loses its internet connection, goes into offline mode, or when the email has an attachment that is too large for the server to accept. Open the stuck email, check its size, and make sure Outlook is online. Delete or move it to Drafts if needed, then resend.
How do I fix Outlook not sending emails due to wrong server settings?
Go to File > Account Settings > Account Settings, select your account, and click Change. Then click More Settings and verify your SMTP server address, port number, and encryption type match your email provider’s requirements. For most providers, port 587 with TLS encryption is correct.
Does antivirus software cause Outlook to stop sending emails?
Yes. Some antivirus programs scan outgoing mail and block the connection if they detect something suspicious or if they are misconfigured. Temporarily disabling the antivirus to test is the fastest way to confirm this. If that is the cause, add Outlook.exe as a trusted application in your antivirus settings.
Why does Outlook send emails in Safe Mode but not normally?
This means a third-party add-in is interfering with the sending process. Go to File > Options > Add-ins, open COM Add-ins, and disable them all. Then re-enable them one at a time, testing after each one, to find which add-in is causing the conflict.
How do I fix Outlook not sending emails after a password change?
Go to File > Account Settings > Account Settings, click on your account, then click Change. Update the password field with your new password and save the changes. Outlook stores your old password and keeps failing authentication until you update it manually.
