Misunderstanding of MUPDATE ?

[Christian Schulte]

Hello,

I am searching for a solution which makes the following possible in an 
easy and simple way:

I have cyrus-2.2 running on machine "A". It is a complete cyrus-2.2 
installation with hierarchysep, virtdomains, altnamespace turned on and 
it is being configured like:


./configure --with-openssl=/usr \
             --enable-netscapehack \
             --with-sasl=/usr \
             --with-bdb-libdir=/usr/lib \
             --with-bdb-incdir=/usr/include \
             --with-cyrus-group=bin \
             --with-cyrus-user=cyrus \
             --without-krb \
             --with-idle=idled \
             --with-notify=no \
             --prefix=/usr/local/cyrus2 \
             --exec-prefix=/usr/local/cyrus2 \
             --with-cyrus-prefix=/usr/local/cyrus2 \
             --enable-listext \
             --enable-annotatemore \
             --with-pidfile=/var/run/cyrus-master.pid \
             --with-statedir=/var/cyrus-state \
             --with-syslogfacility=MAIL

Authentication is setup with auxprop mysql. Also running on machine "A" 
is sendmail which has cyrusv2 configured as the local mailer and does 
local delivery with the /var/imap/socket/lmtp socket. sendmail is linked 
with sasl2 and SMTP_AUTH feature is configured to use auxprop mysql also.

Currently machine "A" is the only mailserver. There is no secondary MX 
and all POP/IMAP accounts are accessed on this machine. If machine "A" 
is down for some reason all email services are offline. Even delivery of 
emails does not work so that if sending an email to one of the domains 
machine "A" is mx for people are getting delivery warnings.

What I need to do is to setup a second machine "B" which can be used 
simultanously for all email services. Machine "B" will run a secondary 
mx which will forward everything to machine "A". So machine "A"'s 
sendmail will be the only smtp-server which will do local delivery to 
cyrus. As I read into MUPDATE I think machine "A" will be called the 
backend server ? This machine holds the mail spool.  As of my 
understanding of MUPDATE I can only setup a cyrus installation on 
machine "B" to which my users can do IMAP/POP connections which 
internally accesses machine "A"'s mail spool over MUPDATE protocol ? 
Does that mean that if machine "A" is down POP/IMAP connections to 
machine "B" will also be refused ?
So I cannot setup a redundant cyrus system using MUPDATE ?
Of course if machine "A" goes down no more mails can be delivered to 
cyrus so the content of machine "A"'s mail spool cannot change either. 
But does the cyrus installation on machine "B" hold a cache to the 
complete mailstore on disk if all users would access the mail store by 
connecting to machine "B" ?
What I would need is a mechanism similar to the mysql replication 
feature!  Any solutions ?


Thanks for your answers!

--Christian--