Why do my Gmail attachments keep failing?

Last reviewed: September 23, 2026 · Markdown version

"Failing" covers several different failures, and they have different fixes. Work down this list in order. Every Google limit quoted here is cited to the Google page it came from.

1. It is over 25 MB

"For personal Gmail accounts, the limit is 25 MB." Google words the trigger as your "total attachment size", so it is the whole message's attachments together, not each file (Send attachments with your Gmail message, read 23 September 2026). That page does not say whether the 25 MB is measured before or after encoding.

Gmail does not refuse outright: it "automatically removes the attachment and adds it as a Google Drive link in the email". So the message sends and the recipient gets a link. For Drive files, Gmail "checks to see if your recipients have access to the file" and, if they don't, prompts you to change the sharing settings before sending (Send Google Drive attachments in Gmail, read 23 September 2026). If someone says your attachment "didn't come through", check whether it became a link.

2. The file type is blocked

Gmail refuses a long list of file types, and it refuses them "including their compressed form (like .gz or .bz2 files) or when found within archives (like .zip or .tgz files)" — so zipping does not get around it. The list includes .exe, .apk, .bat, .cmd, .dll, .iso, .jar, .js, .msi, .scr, .vbs and many more. The error reads: "This message was blocked because its content presents a potential security issue" (File types blocked in Gmail, read 23 September 2026). Google's own tip, if you are sure the file is safe, is to ask the sender to upload it to Google Drive and send it as a Drive attachment.

3. The virus scanner

"Attachments in Gmail messages you send and receive are automatically scanned for viruses" (Anti-virus scanning attachments, read 23 September 2026). Sending an infected file gives you a "Virus detected!" error with the choice to send without it. On an incoming message Gmail "will reject the message and let the sender know", and if it is already in your inbox "you won't be able to download the attachment". There is also a transient case — scanners "temporarily unavailable" — where Google's advice is to try downloading the attachment later.

4. Your storage is full

Google is direct about this one: "If you reach your storage limit, you can’t send or receive attachments" (same attachments page). Its storage page goes further — at the limit you won't be able to "send or receive emails in Gmail" (Manage your storage in Drive, Gmail & Photos, read 23 September 2026). If sending small text emails also fails, this is your answer, not the attachment. What the storage warning means.

5. The upload did not finish

A "Couldn’t send message" error can mean one or more files "didn't upload to Drive", and Google's fix is to "remove or re-add the attachment". If attachments won't upload at all on a computer, its checklist is a supported browser, another browser, and switching off any browser proxy (same attachments page).

6. The recipient's limit, not yours

For work and school accounts, Google says the Workspace administrator "sets the attachment sending limits and attachment receiving limits" (same attachments page), so their ceiling is not necessarily yours. A file that sends fine to one person and bounces from another is worth checking against this.

The habit underneath

If attachments fail and the account is also near full, the two symptoms share a cause: years of heavy mail nobody decided about. Google's own cleanup tip is to "delete unneeded large attachments" and to empty Trash and Spam regularly (same attachments page). Finding them.