[exim] why use virtual hosts in/with exim

Hi all,



I'm trying to figure out if/when I would need to configure exim (4.54) to
support/use virtual hosts. If I have this line configured - domainlist
relay_to_domains = *.domain1.net : *.domain2.org : *.domain3.de :
*.domain4.de , why would I need to configure for virtual hosts? This is
probably a broad/open question, but I do not know enough about the use of
virtual hosts in exim (or any MTA for that matter) to be more specific.
Sorry.



I have several domains I would like to configure exim to accept mail for,
but I do not know if I really should configure for virtual hosts, or if the
domainlist relay_to_domains will do the job.



Could somebody show me a directory layout of a virtual host used in exim?
I'm also wondering if each virtual host setup would have it's own aliases
file. ? I'm also using IMAP and the Maildir format, which I suspect is
relevant to my questions, in regards to a virtual host configuration.



Maybe somebody knows of a good (detailed) explanation (with examples?) of
how to configure virtual hosts in exim?



Thanks in advance!

Robert