[imp] Cannot download large folder

[Chuck Hagenbuch]

Quoting Andrew Morgan <morgan at orst.edu>:

> A more useful question might be, "Why does it require so much memory  
> to download a folder and how can the memory footprint be reduced?"   
> Note - I can trigger this error on my system also with a mailbox  
> that is approximately 1/3 my php memory limit.

If someone wants to trace this a bit, that'd be great.

-chuck