[Exim] socks proxy problem

I use a Debian/GNU Linux computer on a local network (private IP addresses).
This LAN is connected to the internet via a socks proxy.
In this configuration, none of the programs I usually use (ftp, telnet,
fetchmail, etc.)
is working.
Hopefully, I discovered a small program, tsocks, that 'provides transparent
network access through a SOCKS version 4 or 5 proxy', as the documentation
says.
I just have to type 'tsocks fetchmail' instead of 'fetchmail' to get it work.
But when I want to send an email with my Mail User Agent (mutt), it calls
the Mail Transfer Agent (exim) automatically. Then, exim identify the email
adress as a remote one and try to connect to the SMTP server. In my case,
the SMTP server is behind the proxy. As exim is not 'socksified', when it tries
to reach te SMTP server, I get this error message in the
/var/log/exim/mainlog :
'no route to host'.
My question is: how to socksify exim or is there another way to solve my
problem.

Thanks in advance.
Guillaume Oriol.