/usr/lib/courier-imap/etc/pop3*

remove

in /command
qmail.init -> /var/service/dt-run/dt-service.init

in /service
qmail -> /var/service/qmail

add-service.sh - qmail qmail-smtpd qmail-pop3d qmail-qmqpd qmail-qmtpd

$PATH
/usr/local/jdk/bin:/usr/lib/courier-imap/sbin:/usr/lib/courier-imap/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/command:/var/qmail/bin:/usr/local/bin:/usr/X11R6/bin:/root/bin

qmlog -> /var/service/qmail/log/main/current

ln -s /home/vpopmail/etc/tcp.smtp.cdb /service/qmail-smtpd/tcprules.cdb

squirrelmail
$imap_server_type       = 'courier';
$invert_time            = false;
$optional_delimiter     = '.';

$default_folder_prefix          = 'INBOX.';

in /etc/squirrelmail/config.php

run /usr/share/squirrelmail/config/conf.pl

Some linux systems don't like the way qmail uses "errno":

#####################
./load auto-str substdio.a error.a str.a
substdio.a(substdo.o)(.text+0x43): In function `allwrite':
: undefined reference to `errno'
collect2: ld returned 1 exit status
make: *** [auto-str] Error 1

To fix this, edit the error.h file in the qmail source code. Add this after 2, before the line saying "extern int errno;":

#include "errno.h"

After you add that, do "make setup check" again.