As I understand it, mbx is more memory efficient than mbox.
mbx is more memory-efficient than mbox, but that's only because there is no need to convert UNIX-style LF-only strings to Internet standard CRLF strings since mbx is native CRLF.
With the exception of very large message texts, the resulting memory (and CPU) savings is generally too small to notice.
There are system-wide resource restrictions on RAM usage preventing any user from utilizing more than 8 MB of RAM via SquirrellMail. My Sent folder would always exceed this amount when I selected "View All"--there are over 3700 emails stored there. I continue to get the error after the conversion to mbx.
In a best case scenario, 8MB means that there is only about 2K of per-message memory for a 3700 message mailbox. Of course, there is no such thing as a best case scenario, since there are more users of memory that per-message memory.
You were able to open the mailbox since the basic per-message data (message status, sizes, internal dates) isn't that big. But the "view all" probably did an RFC2822/MIME parse of all 3700 messages, and that amount of data is much more than 8MB.
Don't forget, once the IMAP server does an RFC2822/MIME parse, it remembers those results instead of re-doing the parse over and over again.
-- Mark --
http://staff.washington.edu/mrc Science does not emerge from voting, party politics, or public debate. Si vis pacem, para bellum.
