Remove large attachments from the mail spool.
Convert the mail spool to a binary format such as mbx that can be parsed and handled more quickly than a straight text file.
Use a larger timeout while waiting for the IMAP read request to complete. cell phone spy
Thick clients such as Outlook have a configurable timeout from 1 minute to 10 minutes... I believe SquirrelMail 2.x has better support for a longer timeout.