This is usually done in the MTA config.
My question is, why would someone want to send a 50MB attachment via mail?
I would rather you set up an FTP account with authenticated access.
--
˙˙˙˙˙˙˙˙˙˙˙˙˙˙˙˙˙˙˙˙˙˙˙
Regards,
David Njuki
@njukey [Google,Twitter,Yahoo]