MAPIWhy Won’t Gmail Attachments Upload?
Attachment problems can happen before the message itself is sent. Gmail first has to accept or upload the file, and different failure messages point to different checks.
Google recommends trying a supported browser or another browser and disabling a browser proxy when desktop attachments will not upload. It also notes that some send failures occur when files fail to upload to Drive.
Key takeaways
- Google recommends using a supported browser and trying another browser when desktop attachment upload fails.
- A configured browser proxy is another item Google tells users to test by disabling it.
- Attachment hosting can be unavailable if a network administrator or internet provider blocks Google's attachment-hosting domain.
- Google also notes that a file may fail to upload to Drive because of insufficient storage, a slow internet connection, or another upload problem.
What it actually means
A Gmail attachment upload failure occurs when Gmail cannot finish adding the selected file to the outgoing message or to the Drive-based flow used for some attachments.
The main explanation
Google's attachment help separates several situations: desktop upload problems, blocked access to Gmail's attachment-hosting domain, and message-send errors where one or more files did not upload to Drive.
Main causes and reasons
1. Browser problem
Google recommends confirming that the browser is supported and trying the attachment in another browser.
How to recognize it
- The issue happens in one browser
- Another browser behaves differently
Why it matters: This is a direct first-line check for desktop attachment upload failures.
2. Browser proxy configuration
Google specifically recommends trying to disable a configured web browser proxy.
How to recognize it
- A browser proxy is configured
- The issue changes after proxy settings change
Why it matters: Google explicitly includes disabling a configured browser proxy among its attachment-upload troubleshooting checks.
3. Attachment-hosting domain is blocked
Google says an administrator or internet provider may block mail-attachment.googleusercontent.com.
How to recognize it
- Attachments fail on a managed or filtered network
- The problem differs on another network
Why it matters: If that domain is blocked, attachments may be unavailable.
4. Drive upload did not complete
Google says a send error can happen because one or more files did not upload to Drive, possibly because storage is insufficient or the internet is slow.
How to recognize it
- Gmail reports that one or more files did not upload to Drive
- Storage is full or the connection is slow
Why it matters: This matters for Gmail flows that depend on a Drive upload.
How to identify your situation
A browser-specific issue is plausible.
Next: Try a supported alternative browser.
The proxy is one of Google's documented checks.
Next: Temporarily disable the browser proxy and retry.
The attachment failed in the Drive upload stage.
Next: Check account storage and connection quality, then remove or re-add the attachment.
The attachment-hosting domain may be blocked.
Next: Ask the network administrator or internet provider about access to the Gmail attachment domain.
What you can do
- Use a supported browser.
- Try adding the attachment in another browser.
- If a browser proxy is configured, test with it disabled.
- If Gmail reports a Drive upload failure, check storage and connection, then remove or re-add the attachment.
- If attachment hosting is blocked by the network, contact the administrator or provider.
Common misconceptions
Google documents browser, proxy, network-domain, storage, and connection causes as well.
Google notes that one or more files may have failed to upload to Drive.
When it may be a bigger problem
If attachments are unavailable because the Gmail attachment-hosting domain is blocked, Google tells users to contact their internet service provider.
Frequently asked questions
What browser check does Google recommend for attachments that will not upload?
Use a supported browser and try adding the attachment in another browser.
Can a proxy stop Gmail attachments from uploading?
Google recommends disabling a configured browser proxy as a troubleshooting step.
Can Google storage affect a Gmail attachment?
Google says a file may fail to upload to Drive because there is not enough space.
Can a network block Gmail attachments?
Yes. Google says an administrator or internet provider may block the domain Gmail uses to host attachments.
Sources
- Send attachments with your Gmail message — Gmail HelpOfficial
Written by Mapiance Editorial Team
The Mapiance Editorial Team researches, writes, reviews, and maintains practical guides and explainers for MAPIANCE.
Reviewed by Mapiance Editorial Team
Published Sep 21, 2026 · Updated Sep 21, 2026 · Verified Sep 18, 2026