Attachment Issues

How to Fix Email Bounces When Sending Large Attachments

Camila Milosovich Sep 25, 2026 869 views

Question details

The user's emails containing a 26.4 MB attachment are being rejected and bouncing back when sent to a specific domain.

How to Fix Email Bounces When Sending a 26 MB Attachment

Product: Email Client / Exchange Online
Device & OS: not provided
Scenario: Sending a large email attachment to a specific recipient domain.
Observed behavior: Messages with the 26.4 MB attachment bounce back as undelivered. However, text-only emails to the same domain and similar large attachments sent to other recipients are delivered successfully.

Before you start

Verify that you have access to a cloud storage account (such as OneDrive, Google Drive, or WPS Cloud) to use as an alternative file-sharing method.

Solution 1Recommended

Share the File Using Cloud Storage (OneDrive)

Bypass email attachment limits entirely by uploading the large file to a cloud service and sharing a secure link instead of attaching the file directly.

Email systems impose strict message-size limits, often capping at 20 MB or 25 MB. Because encoding adds overhead to the file size, a 26 MB file will easily exceed standard limits. Using cloud storage prevents bounce-backs by keeping the email size extremely small.

Open your cloud storage

Log into your OneDrive or preferred cloud storage account via your web browser.

Upload the attachment

Drag and drop the 26 MB file into your cloud drive to upload it.

Generate a sharing link

Right-click the uploaded file and select 'Share' or 'Copy Link' to generate a secure URL.

Send the link via email

Paste the generated link into your email draft, remove the original heavy attachment, and send the message to the recipient.

Share the File Using Cloud Storage (OneDrive)

Delivery Assured: Sending a cloud link ensures your message is treated as a standard text email, guaranteeing it will not trigger attachment size filters on the recipient's server.

Solution 2

Compress the Attachment to Reduce Size

Reduce the total file size below the recipient's maximum message limit using ZIP compression.

Free Microsoft Office alternative

Switch to WPS Office for Seamless Document Sharing

Struggling with Exchange Online limits and bouncing attachments? WPS Office is a free, lightweight alternative to Microsoft Office that comes with built-in cloud sharing capabilities. Easily generate secure links for massive documents instead of sending heavy email attachments.

1. Download and Install: Get WPS Office for free from the official website and install it on your computer.
2. Open Your Document: Open your large document, spreadsheet, or presentation in WPS Office.
3. Share via Cloud Link: Click the 'Share' button in the top right corner to instantly generate a WPS Cloud link, easily bypassing email attachment limits.

Fully compatible with Microsoft Office formats (.docx, .xlsx, .pptx)Built-in WPS Cloud allows you to share massive files via a simple linkFree and lightweight software that won't slow down your deviceIntegrated PDF tools to easily compress documents before sending

Frequently Asked Questions

Why does a 26 MB attachment bounce when the limit is 25 MB?

Email systems must encode attachments (usually using Base64) to transmit them safely over the internet. This encoding process increases the file size by approximately 33%. As a result, a 26 MB file becomes over 34 MB when attached, easily exceeding standard 25 MB or 30 MB limits.

Why did my email go through to other recipients but not this specific domain?

Message-size limits are determined by both the sender's and the recipient's email servers. Even if your email provider allows large attachments, the specific recipient's domain may enforce a stricter, lower limit (e.g., 10 MB or 20 MB), causing the email to bounce only for them.

How can I check my Exchange Online message limits?

If you are an administrator, you can check message size limits in the Exchange Admin Center under Mail flow > Message size limits. End users can typically find their limits by checking their webmail settings or asking their IT department.

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