2.3 to 2.4 Murder upgrade

[Andrew Morgan]

I finally have some time to work on upgrading our Cyrus Murder 
installation from 2.3.16 to 2.4.12.  We have 3 backends, 3 frontends, and 
a mupdate master, all separate systems.

When I upgraded from 2.2 to 2.3, I had to upgrade the backends first. 
Otherwise, the 2.3 frontends would issue commands that the 2.2 backends 
didn't know yet.  I see the following note in the install-upgrade guide:

Upgrading from 2.4.5

     New config option: suppress_capabilities, which takes a space 
separated list of capabilities which will NOT be given in any imap 
capability response. This can be used on frontends to not display 
capabilities that older backends don't have, so clients don't get confused


This leads me to believe that I should upgrade the backends to 2.4 first. 
Is that true?  Has anyone done a Murder upgrade from 2.3 to 2.4 and can 
tell me what order they upgraded the hosts?

Thanks!

 	Andy