Exim error too main files open

Hello Friends

I have some issue with exim in linux whenecer i run my scripts i get error which is mention below
2007-08-06 19:11:14 1II2pe-0000Uv-AC Cannot open main log file "/var/log/exim_mainlog": Too many open files in system: euid=47 egid=12
euid=47 is mailman
egid=12 is mail

please let me why this error comes and how can i solve it
its very very very urgent

Thanks In advance

Thanks
Shri