[exim] Hidden Exim version number

Dear All,

I want to hidden the version number of my exim SMTP server. I am using Exim
4.70 now. But I does not want any one to know the for security reason.

When I telnet to my SMTP server with port 25, I got the following

220 mai.xxx.com ESMTP Exim 4.70 Wed, 15 Sep 2010 18:33:07 +0800

Can I hidden the version number?

Thank you very much!

Michael