Why is Outlook not allowing me to send attachments

Question

Outlook is not allow me to send file that are smaller than 100KB. Why? Is there some kind of setting I need to adjust or turn off/on? Thank You

Answer 1

Did you get any bounce back email? If so, can you please share the bounce email? It contains important diagnostic data that helps shed some light of the root cause. Feel free to redact personal information when you share.

Answer 2

Outlook itself normally limits attachments only when the total message size exceeds the account’s limit (for many internet accounts, about 20 MB; for many Exchange accounts, about 10 MB), not as small as 100 KB. When very small files cannot be sent, the issue is usually elsewhere in the send path.

Check these areas in classic Outlook on Windows:

1. Confirm Outlook is online and connected

• Look at the status bar at the bottom of the Outlook window.
• If it shows Disconnected, Working Offline, or Trying to connect…, Outlook cannot reach the mail server.
• Go to the Send/Receive tab on the ribbon.
• In the Preferences group, select Work Offline once to toggle back online.
• Then try Send/Receive again and resend the message.
• If still not sending, verify internet access by opening a browser and visiting a site such as microsoft.com or bing.com as described in the article.

2. Check for a stuck or oversized message in Outbox Even if the file being sent now is small, a previously stuck large message can block the Outbox.

• Go to the Outbox folder.
• Open each stuck message, starting with the oldest.
• If any message has large attachments (for many providers, larger than about 20 MB), remove the attachment or delete the message.
• After clearing any large or stuck messages, try sending a new test message with a small attachment.

3. Consider provider or server-side limits

• Many providers (including Outlook.com, Gmail, and Exchange Online) enforce message-size limits. For internet accounts, the typical limit is about 20 MB per message; for Exchange accounts, the default is about 10 MB.
• If using a work or school account, the Exchange administrator may have set stricter limits. In that case, the administrator can review and adjust the Maximum send size or mailbox Message size restrictions in Exchange, as described in the documentation.

4. If attachments are large in general

• For larger files, use the guidance in the attachment-size article: compress the file (ZIP), upload to a cloud or shared location (such as OneDrive or SharePoint), and send a link instead of attaching the file directly.

If Outlook is online, the Outbox is clear, and the account’s server limits are not exceeded, but even very small attachments still cannot be sent, the next step is to contact the email provider or support channel for that account to check for account-specific restrictions or known issues.

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References:

• I can't send or receive messages in Outlook
• Reduce attachment size to send large files with Outlook
• Attachment size exceeds the allowable limit error when you add a large attachment to an email message in Outlook
• Event ID 27 when sending attachments outside of Outlook fails
• Outgoing emails with attachments undelivered as spam - Microsoft Q&A
• How to increase attachment size limitation - Microsoft Q&A