When I attach a file to be sent in an email is the progress bar that displays
the file being encoding to MIME
or
is the file being upload to a server?
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Sign up to join this communityMost likely uploaded to the server, since that is the slowest operation. Any special encoding done to the file probably takes fractions of a second on Google's beefy mail servers. Either way it is probably not wise to try to interrupt it if you want your file attached.
generally mimetypes are part of the file header gmail does flag certain mimetypes and i believe it checks the initial mimetype before uploading then uploads it to the server then searches the file file for other mimetypes eg archives get searched for executable files and for source files
so the loading bar is generally it being uploaded to the server