Incompatibilities on the sender's side often cause attachments to appear inline. Please follow the steps below to determine if Gmail is causing the error.
If the attachment in your message is being displayed inline, check the message headers to determine whether this behavior was intended.
We suggest performing a search in your headers for the term "Content-Disposition:". (Tip: You can use your browser's "Find" function by clicking Ctrl + F on a PC or Command + F on a Mac.) If the word "inline" appears next to the "Content-Disposition:" field, the sender's mail client or webmail provider intended to include the attachment as inline, and not downloadable.
Content-Disposition: inline; filename="Letter.txt"
If you wish to receive the attachment as a downloadable file, we suggest contacting the sender for further information.
If your message's "Content-Disposition:" field does not say "inline," you can send the headers to the Gmail Team for further investigation.