I'm still having no luck increasing maximum attachment size. I create file: /etc/exim4/exim4.conf.localmacros I leave it default permissions: -rw-r--r-- 1 root root It has a single line: MESSAGE_SIZE_LIMIT = 200M followed by CR. And I restart exim: # invoke-rc.d exim4 reload But: # exim -bP | grep size bounce_return_size_limit = 100K header_line_maxsize = 0 header_maxsize = 1048576 message_size_limit = 50M