Q0415 - Exim/exim GitHub Wiki
Q0415
Can I use my existing alias files and forward files as well as procmail and effectively drop in Exim in place of Sendmail ?
Yes, as long as your alias and forward files don't assume that pipes are going to run under a shell. If they do, you either have to change them, or configure Exim to use a shell (which it doesn't by default).