You may get error alerts like "Attachment failed" or "Can't Attach file" while sending a Gmail message with an attachment. So, to solve this, make sure you're using a supported browser, or try adding the attachment in another browser. Moreover, the web browser proxy might be causing the issue Gmail won't send attachments. So, try disabling the proxy server. Now, look for 'Use a proxy server' for your LAN setting and deselect the box beside it.
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