[Exim] Changing the spool location or multiple exims sharing…

Hi

Is there anyway I can set the spool directory at runtime rather than setting
it in the exim binary?

I need to replace a highly customized sendmail set-up that has different
sendmail configurations for each user, while I have almost worked it out (I
would have to have a custom exim config file for each one and bind to their
IP)

I don't know the effect running 10/15 exim's using the same binary will
have? I.E. they are hard coded to use the same spool directory etc... will
this work having multiple ones?

Currently each user has their own etc,mail,spool directorys in their home
directory and sendmail is called using inetd so depending on what domain is
called sendmail runs a custom sendmail.cf. Id really like to replace this
with exim but want to do the migration with as much ease as possbile

Thanks
Darren