Attachment Issues

Fix Viva Engage Post by Email Fails with Large Attachments

Amos Gikunda Oct 13, 2026 868 views

Question details

The user is experiencing failures when attempting to post to Viva Engage via email with a 2 MB attachment, despite this size being well within official network limits.

How to Fix Viva Engage Post by Email Failing with Large Attachments

Product: Viva Engage
Device & OS: not provided
Scenario: Publishing a post and sharing files to a Viva Engage network using the post-by-email functionality.
Observed behavior: The post fails to publish or process the 2 MB attachment, even though published limits support much larger file sizes (up to 100 MB or 5 GB depending on the network type).

Before you start

Verify that your internet connection is stable and ensure the attachment is not a restricted file type (such as an executable .exe file) that might be automatically blocked by standard email security filters.

Solution 1Recommended

Verify Email Filtering and Tenant Configurations

Check if your organization's email processing rules or attachment filters are blocking the file before it reaches Viva Engage.

A 2 MB attachment is well below the published Viva Engage limits (100 MB for Basic, 5 GB for Enterprise). Therefore, the blockage is typically caused by Microsoft 365 Exchange mail flow rules, tenant-level security configurations, or specific attachment filtering rather than Viva Engage itself.

Confirm attachment type

Check the file extension of your 2 MB attachment. Ensure it is a standard document or image format (like .pdf, .docx, or .jpg) and not a potentially malicious file type.

Test with an alternative file

Attach a different, smaller, and safe file (e.g., a simple text document) to a new email and send it to the Viva Engage address to see if the issue is file-specific.

Review bounce messages

Check your email inbox for any Non-Delivery Reports (NDR) or bounce-back messages, which often contain specific error codes explaining why the email was rejected.

Verify Email Filtering and Tenant Configurations

Alternative Upload Method: If you need to share the file urgently, log in directly to the Viva Engage web or mobile application and upload the attachment natively to your post.

Solution 2

Escalate to Your Microsoft 365 Administrator

If email filters are not the cause, the issue may be a backend service limitation or a temporary outage requiring administrative support.

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Frequently Asked Questions

What is the maximum attachment size limit for Viva Engage?

For Viva Engage Enterprise networks, the attachment limit is up to 5 GB. For Basic networks, the limit is 100 MB. A 2 MB file is well within normal operational parameters.

Why would a small file fail to post by email?

Failures for files under the size limit are typically caused by organization-level email processing rules, strict attachment filtering policies, incorrect sender permissions, or a backend Microsoft 365 service issue.

How can I bypass the post-by-email attachment error?

The quickest workaround is to access Viva Engage through your web browser or the desktop/mobile application, create a new post manually, and upload your attachment directly from your device.

Who can fix persistent Viva Engage email integration issues?

If the issue persists across multiple files and users, your organization's Microsoft 365 administrator will need to investigate Exchange mail flow rules or open a dedicated support ticket with Microsoft to resolve the service disruption.

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