ErrorFindly
0x80042109OfficeHigh

Error 0x80042109 — Outlook Sending Timeout | Microsoft Office Fix

Microsoft 365Office 2021Office 2019Office 2016

What Does 0x80042109 Mean?

Outlook timed out waiting for the outgoing (SMTP) mail server to respond when attempting to send an email.

Real-World Causes

  1. 1SMTP server address or port misconfigured
  2. 2Large attachment taking too long to upload
  3. 3Firewall blocking outgoing SMTP port
  4. 4ISP throttling email sending traffic

Symptoms

  • ⚠Emails stuck in Outbox and won't send
  • ⚠Timeout error when clicking Send/Receive
  • ⚠Sending progress bar stalls
  • ⚠Error appears after long delay

DIY Fix

Beginner-friendly steps you can try at home

  1. 1Verify SMTP server settings and port number
  2. 2Reduce attachment size or use cloud sharing links instead
  3. 3Increase server timeout setting in Outlook
  4. 4Try sending without attachments to isolate the issue

Advanced Fix

For experienced users and IT professionals

  1. 1Test SMTP connectivity using telnet on the configured port
  2. 2Check if ISP blocks port 25 and switch to port 587
  3. 3Disable SMTP authentication temporarily to test
  4. 4Review antivirus email scanning settings

Frequently Asked Questions

Why can I receive but not send emails?
Sending and receiving use different servers and ports. Your incoming (POP3/IMAP) settings may be correct while your outgoing (SMTP) settings are wrong. Verify SMTP server, port, and authentication settings.
What's the maximum email attachment size?
Most email providers limit attachments to 20-25 MB. Microsoft 365 allows up to 150 MB. For larger files, use OneDrive, Google Drive, or other cloud sharing services.

Related Error Codes

0x80042108Outlook Receiving Timeout0x800CCC0EOutlook Connection Failed0x800CCC67SMTP Server Error

About the Author

Windows Troubleshooting Team

Verified against official Microsoft documentation and real-world diagnostic data. Error behavior confirmed across Windows 10, Windows 11, and Windows Server.