[imp] Crazy memory usage when viewing attachments

[patrick]

I'm noticing that IMP requires an incredible amount of RAM to display
a message with a relatively large attachment. For example, on of our
customers was complaining that she couldn't open a message that was
was 1.4MB in size. Our memory limit was set to 50MB, and Apache was
running out of memory when viewing this message. Increasing it to 64MB
seemed to solve it, but I'm trying to comprehend what in IMP is
causing it to required more than 35 times the size of the message in
order to view it?

We have the following setup:

Horde 3.1.3
IMP 4.1.3
PHP 4.3.11
Apache 1.3.36
mod_ssl 2.8.27
eAccelerator 0.9.5

Any ideas? What is the process by which IMP loads in a message?

Patrick