[imp] horde cache config with IMP 3.2 / multiple imap sessions per page hit Imp 3vs4

[Michael Yingbull]

Could one of the development types or other lurking guru clarify for me 
what the:

$conf['cache']

parameter tree in the horde/config/horde.php configuration file fully 
relates to?  The comments indicate it will cache commonly used objects - 
does this have an impact on IMAP connection requirements in IMP 3.2?   
Will having this enabled  mean less imap connections per page hit?  What 
does it cache?

I recall reading that IMP 4.x was more polite with the IMAP server in 
not needed as many IMAP connections per page hit (I saw something in the 
config about the folder  caching, etc).   How many connections to the 
IMAP server does IMP 4 need to do per page display, in most common cases?