In the same spirit, and for the lazy who'd rather not issue all those commands by hand: If you have a *recent* copy of Mozilla, and set it up to access an IMAP account, you can watch the protocol at work by doing the following (that's how they debug the MailNews component). First set two environment variables -- in tcsh:

[localhost:~] fz% setenv NSPR_LOG_MODULES IMAP:5
[localhost:~] fz% setenv NSPR_LOG_FILE ~/imaplog.txt

(you can unset them later with unsetenv NSPR_LOG_MODULES; unsetenv NSPR_LOG_FILE). Then launch Mozilla from the command line:

[localhost:~] fz% /Applications/Mozilla.app/Contents/MacOS/mozilla-bin

(assuming this is where you put Mozilla.app), and go check your mail. This will create a file 'imaplog.txt' in your home directory, which will record the imap session -- you can also watch it unfold in real time with

[localhost:~] fs% tail -f imaplog.txt

(This works only since 1.3alpha or so. In earlier builds the procedure was different.)