Is your send/receive interval set too closely? Try setting it to 10 minutes
or turning it off while you're sending such a large file. If you're scanning
the file with antivirus, turn that off as well though it's possible it may
require that you uninstall/reinstall omitting the email scanning
integration.
Thinks for letting us know that your news service provider has extreme
retention. But nobody here is downloading binary content. It is a help
forum, and assistance should be provided in a *timely* manner!