v2.1's imap/pop3 processes are linked with OpenSSL by default, because of imapc/pop3c storages. I wonder if you notice any actual (system-global) memory usage reduction when compiling without those and you have thousands of imap processes?
./configure --with-storages=mdbox sdbox maildir mbox cydir I guess I could try it myself also but maybe someone else wanting to reduce memory usage is quicker? :) Related to that, you can look at where imap processes' memory goes with: http://dovecot.org/tools/linux-maps-parse-imap.pl I don't know how much memory those (writable!) file-backed memory areas actually use per-process. Maybe nothing, maybe something..
