Exim4 and Message could not be sent because its size exceeded the server's limit

["Charlie Grosvenor" <charlie@cgrosvenor.co.uk>]

I have just upgraded to exim4 and now I cannot send large messages (50mb), I
have increased the limit in the file:

    /etc/exim4/conf.d/main/01_exim4-config_listmacrosdefs

    MESSAGE_SIZE_LIMIT = 1000M

and updated the main configuration file update-exim4.conf and restarted exim
and it makes no difference. How do I go about getting rid of this limit?

Thank you