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Outlook – Troubleshooting Emails not sending

Summary

If Outlook has stopped sending emails, this guide will help you identify and fix common issues. Steps include checking for sync errors, reducing mailbox size, and identifying large messages that may be blocking the Outbox. Follow the guide below before raising an incident.

Resolving Outlook Send/Receive Issues

Please look for any error messages these usually appear in the banner at the top of outlook.

Click into the send and receive tab (shown below)

Then click on ‘send/receive all folders’ (shown below) and make a note or take a print screen of any error messages.

Next check to see if outlook is connecting to the server, you can do this by hovering your mouse over where the arrow shows in the image below.

Next check your internet connection and restart your laptop and router.

Check for Stuck Items in the Outbox

Navigate to the outbox folder, if messages are stuck open the message and click send. If this doesn’t work try deleting the message and recreating it.

Confirm Mailbox Size Isn’t Causing the Issue

Large mailboxes can sometimes prevent sending or receiving emails.To check and reduce mailbox size:

In Outlook, go to File > Tools > Mailbox Cleanup

Select View Mailbox Size to check if it’s nearing the limit.

Still under Mailbox Cleanup, click Find items larger than and enter 250 KB, Review and delete any unnecessary large items, then empty Deleted Items. This should free up space. Restart out look and try resending the message.

If the Issue Persists

Raise a ticket on fresh including what you’ve tried and any information you have on the error.

FAQ’S

Q: What’s the mailbox size limit in Outlook?

A: For Microsoft 365 mailboxes, the standard limit is usually 50 GB unless otherwise configured.

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