Hi,
functions/Misc/checkmail is a function that is supposed to output a 
message when new mail is detected (either with function arguments, or 
else $MAILPATH, or else $MAIL, or else /var/spool/mail/$LOGNAME

I use MAILPATH=~/Mail and have many files (mbox) in that directory.

That function doesn't work. That is because 

if [[ -d "$file" ]] then
    file=( "$file"/**/*(.ND) )
    if (($#file)) then
        checkmail "${^file}\?$message"
    fi
fi

checkmail will be called with an array that contains all the files in 
MAILPATH
but 

for file in "${@:-${mailpath[@]:-${MAIL:-/var/spool/mail/$LOGNAME}}}"

will give a scalar. file will be a string containing all the files.
So, test -s "$file" -a -N "$file" will be 
test -s file1 file2 file3 -a -N file1 file2 file3, and will never succeed

I found a way to solve this by splitting the function arguments :

for file in "${(z)@:-${mailpath[@]:-${MAIL:-/var/spool/mail/$LOGNAME}}}"

but I'm not sure if it is the better way.

Another bug I found was :
checkmail "${^file}\?$message"

if message is "Hello", this gives

checkmail file1 file2 file3?Hello

By removing the double quotes, this works fine
checkmail ${^file}\?$message
gives
checkmail file1?Hello file2?Hello file3?Hello

Here is a patch containing fixes for the two problems
arno

Index: Functions/Misc/checkmail
===================================================================
RCS file: /cvsroot/zsh/zsh/Functions/Misc/checkmail,v
retrieving revision 1.4
diff -n -u -r1.4 checkmail
--- Functions/Misc/checkmail	29 May 2001 17:54:39 -0000	1.4
+++ Functions/Misc/checkmail	15 Sep 2006 17:38:38 -0000
@@ -1,4 +1,4 @@
-#! /usr/local/bin/zsh
+#! /usr/bin/zsh
 #
 # This autoloadable function checks the folders specified as arguments
 # for new mails.  The arguments are interpreted in exactly the same way
@@ -10,15 +10,16 @@
 #
 
 local file message
+setopt noshwordsplit
 
-for file in "${@:-${mailpath[@]:-${MAIL:-/var/spool/mail/$LOGNAME}}}"
+for file in "${(z)@:-${mailpath[@]:-${MAIL:-/var/spool/mail/$LOGNAME}}}"
 do
 	message="${${(M)file%%\?*}#\?}"
 	file="${file%%\?*}"
 	if [[ -d "$file" ]] then
 		file=( "$file"/**/*(.ND) )
 		if (($#file)) then
-			checkmail "${^file}\?$message"
+			checkmail ${^file}\?$message
 		fi
 	elif test -s "$file" -a -N "$file"; then  # this also sets $_ to $file
 		print -r -- "${(e)message:-You have new mail.}"