Send & Receive Issues

How to Fix Outlook Cannot Send Emails Issue

Bushra Parveen Sep 29, 2026 868 views

Question details

The user is unable to send emails from Outlook and needs to know the correct troubleshooting steps, including whether a specific instant messaging registry setting controls regular email delivery.

How to Fix Outlook Cannot Send Emails Issue

Product: Microsoft Outlook
Device & OS: not provided
Scenario: Attempting to send regular emails from the Outlook desktop client, but the messages fail to deliver or get stuck.
Observed behavior: Emails are not being sent for an extended period. There is confusion about whether the DefaultIMApp registry key impacts ordinary email sending.

Before you start

Ensure you have a stable internet connection and try accessing your email account through webmail to rule out temporary server outages before changing any settings.

Solution 1Recommended

Troubleshoot Regular Email Delivery in Outlook

Follow these standard troubleshooting steps to fix issues preventing Outlook from sending ordinary emails.

Regular email sending issues are typically caused by connection problems, full mailboxes, or messages stuck in the Outbox. The registry setting for instant messaging (DefaultIMApp) does not affect ordinary email delivery.

Check the Outbox folder

Open Outlook and click on the 'Outbox' folder in the left navigation pane. If there are messages stuck here, drag them to the 'Drafts' folder, open them, and try sending them again, or delete them if they contain overly large attachments.

Test your account connection

Go to the 'Send / Receive' tab on the ribbon and click 'Send/Receive All Folders'. Look at the progress dialog box for any specific error codes related to the outgoing server (SMTP).

Verify mailbox storage limit

Click 'File' > 'Info' and check the 'Mailbox Settings' section. If your mailbox is full, you will need to delete old emails or empty your 'Deleted Items' folder to resume sending messages.

Install Office updates

Navigate to 'File' > 'Office Account' (or 'Account'), click on 'Update Options', and select 'Update Now' to ensure Outlook is running the latest version with all bug fixes.

Troubleshoot Regular Email Delivery in Outlook

Webmail Test: If Outlook still cannot send emails, log in to your email provider's webmail interface (e.g., Outlook.com or Gmail) and try sending a message from there to confirm your account is not locked.

Solution 2

Fix Instant Messaging Integration via Registry Editor

Use this solution only if your issue is specifically about Outlook's integration with IM apps like Teams or Lync failing to display online status.

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Frequently Asked Questions

Why are my emails getting stuck in the Outlook Outbox?

Emails usually get stuck in the Outbox due to a lost internet connection, an incorrect outgoing server (SMTP) password, or because the email contains an attachment that exceeds the server's size limit (typically over 25MB).

Will changing the DefaultIMApp registry key fix my email delivery?

No. The DefaultIMApp registry key (located under HKEY_CURRENT_USER\SOFTWARE\IM Providers) only controls which application provides presence and instant messaging features inside Outlook (like Microsoft Teams). It does not affect ordinary email sending or receiving.

How do I check if my Outlook mailbox is full?

You can check your storage capacity by clicking 'File' > 'Info' in Outlook. Look under the 'Mailbox Settings' section to see a visual bar indicating how much space you have used and how much is remaining.

What should I do if Outlook is offline or disconnected?

Check the status bar at the bottom of the Outlook window. If it says 'Working Offline' or 'Disconnected', go to the 'Send / Receive' tab on the ribbon and click the 'Work Offline' button to toggle it off and reconnect to the server.

Outlook & Email Problems