Take the 2-minute tour ×  I have a vague notion but I'm not
clear on the difference between local domains and "relay
domains"  I believe that local domains are "localhost" and any
other aliases you set the server up to mean "self".  I believe
"relay" domains are "everything else?" Like if a DNS has
foobar.com point to this server, then foobar.com is a relay
domain? I am not sure about this point.  In the exim setup file
- (exim4.template.conf) What does it mean "fallback MX or mail
gateway for domains" - what is fallback mx? Does it mean your
server is like a DNS server of sorts?  share|improve this
question  2 Answers 2  Local domains are any domains which are
on the server and mail to those addresses is delivered to a
local mailbox (or a local alias), eg. john@example.com and
john@example2.com both deliver to john's mailbox on the server,
no separation.  A virtual domain is similar, but there will be
separation (eg. /var/spool/mail/example2.com/john is a mailbox).
A relay domain is one which your mailserve