Current situation: If I create a message, attach a huge file, and quickly hit the "Send" button, the message is sent without the file since it wasn't uploaded yet. I cannot think of any reason why anyone would want that. Who would attach a file that they didn't want sent? Yes, a checkbox appears while the upload is going on that says "Auto-send when upload is complete", but why doesn't the "Send" button do that by default? To me, the perfect solution would be this: When files are being uploaded, have a status bar just to the right of the "Send" button indicate the overall status of the uploads (so that the user doesn't have to scroll down to see the status). Change the behavior of the "Send" button so that if uploads are not complete it functions the same as the "Auto-send when current uploads are complete" checkbox. In addition, if uploads are not complete when the users hits the "Send" button, say to the right of the button "File upload in progress! Do not close this page until uploads are complete!" When the upload is complete, change the text to say "Upload complete. OK to close or move away from this page." If you (as the designers) think that some people might want to attach files but not send them, then I think the best compromise is changing the current checkbox to a green button like the current "Send" button. Have the 2 buttons be labeled something like "Only send files already uploaded" and "Auto-send when current uploads are complete". Include the status bars and warnings as I suggested above. I think that either of these changes would explain things SO much better to the users. Thanks!