Emails Not Sending or Receiving? Common Fixes Explained

📧 Outlook Not Sending Emails? Fix It Fast in Microsoft 365

When Outlook won’t send mail, it’s usually one of a handful of causes: connectivity, a stuck message, add-in conflicts, profile corruption, or security tools blocking traffic. Work through these steps in order for the quickest, most reliable result.

🔁 1. Confirm the Basics
• Open a website on the same device to verify internet access
• In Outlook, toggle Send/Receive > Work Offline (ensure it’s OFF)
• Check mailbox size; empty Deleted Items and Sent Items if full

📮 2. Clear a Stuck Outbox
• Go to Outbox and open the message marked Trying to send
• Remove oversized attachments (keep under ~20–25 MB)
• Save locally, delete from Outbox, then send a small plain-text test email

🧰 3. Start in Safe Mode to Bypass Add-ins
• Close Outlook → press Windows + R → type outlook.exe /safe
• If sending works, disable add-ins: File > Options > Add-ins > COM Add-ins > Go…
• Re-enable one by one, test after each to find the culprit

🔐 4. Re-authenticate and Clear Cached Credentials
• File > Office Account — confirm you’re signed in to the correct Microsoft 365 account
• Close Outlook → Control Panel > Credential Manager > Windows Credentials → remove old Outlook/Microsoft Office entries
• Reopen Outlook and complete sign-in/MFA

🛠️ 5. Repair (or Recreate) the Outlook Profile
• File > Account Settings > Account Settings… > Email > Repair (Quick Repair)
• If still failing: Control Panel > Mail > Show Profiles > Add… → create a new profile and test
• Allow time for the mailbox to fully resync before re-testing send

📤 6. Check Send/Receive Controls & Rules
• Send/Receive > Send/Receive Groups > Define Groups — ensure your account is included and scheduled
• Confirm Work Offline is not enabled
• File > Manage Rules & Alerts — disable rules that delay or re-route outgoing mail

🔄 7. Update Office and Windows
• File > Office Account > Update Options > Update Now
• Run Windows Update, install pending drivers/patches, then reboot

🛡️ 8. Review Antivirus & Firewall Policy (Safely)
• Keep real-time protection ON, but turn off email content scanning temporarily to test
• Ensure Outlook and Microsoft 365 endpoints aren’t blocked or SSL-inspected
• Need protection set up correctly? We can supply and configure reputable endpoint security (ask us for licences)

🧩 9. Network & Attachment Checks
• Send without attachments or share a OneDrive/SharePoint link instead
• Test from a different network (e.g., mobile hotspot) to rule out ISP/router filtering

🩺 10. Advanced Repairs (Only If Needed)
• Run Inbox Repair Tool (scanpst.exe) on the OST/PST (close Outlook first)
• Create a fresh Windows user profile if the OS profile is corrupted

🏢 For Microsoft 365 Admins (Tenant-Side)
• Check Service health for Exchange Online incidents
• Review mail flow rules, outbound anti-spam limits, and quarantine
• Confirm active Exchange Online licence assignment
• Validate connectors (hybrid/relay) and TLS settings if used

💡 Still Stuck? We Can Help
If sending is still failing, it may be policy- or profile-level. Call IT Mate offers remote and onsite support across Australia — PAYG or managed — to get email flowing and keep it secure.