> telnet 192.168.20.1 110
Trying 192.168.20.1...
Connected to 192.168.20.1.
Escape character is '^]'.
+OK
USER jayjwa
+OK
PASS s3cr3t
-ERR Authentication failed (bad password?)
Connection closed by foreign host.

May 15 13:51:50 atr2 vmunix: [427685.241713] popa3d[32056]: segfault at fffffffff7f75220 ip 00007ffff7772307 sp 00007fffffffd578 error 5 in libc-2.39.so[7ffff7628000+16f000] likely on CPU 0 (core 0, socket 0)
May 15 13:51:50 atr2 vmunix: [427685.241728] Code: 48 01 d0 c5 f8 77 c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 c4 41 01 ef ff 89 f8 09 f0 c1 e0 14 3d 00 00 00 f8 0f 87 29 03 00 00 <c5> fe 6f 07 c5 fd 74 0e c5 85 74 d0 c5 ed df c9 c5 fd d7 c9 ff c1
May 15 13:51:50 atr2 popa3d[32050]: Authentication failed for jayjwa
May 15 13:54:35 atr2 vmunix: [427849.918832] popa3d[32231]: segfault at fffffffff7f75220 ip 00007ffff7772307 sp 00007fffffffd578 error 5 in libc-2.39.so[7ffff7628000+16f000] likely on CPU 3 (core 1, socket 0)
May 15 13:54:35 atr2 vmunix: [427849.918845] Code: 48 01 d0 c5 f8 77 c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 c4 41 01 ef ff 89 f8 09 f0 c1 e0 14 3d 00 00 00 f8 0f 87 29 03 00 00 <c5> fe 6f 07 c5 fd 74 0e c5 85 74 d0 c5 ed df c9 c5 fd d7 c9 ff c1
May 15 13:54:35 atr2 popa3d[32225]: Authentication failed for jayjwa
May 15 13:55:00 atr2 vmunix: [427874.637699] popa3d[32252]: segfault at fffffffff7f75220 ip 00007ffff7772307 sp 00007fffffffd578 error 5 in libc-2.39.so[7ffff7628000+16f000] likely on CPU 6 (core 5, socket 0)
May 15 13:55:00 atr2 vmunix: [427874.637714] Code: 48 01 d0 c5 f8 77 c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 c4 41 01 ef ff 89 f8 09 f0 c1 e0 14 3d 00 00 00 f8 0f 87 29 03 00 00 <c5> fe 6f 07 c5 fd 74 0e c5 85 74 d0 c5 ed df c9 c5 fd d7 c9 ff c1

diff -Nur popa3d-1.0.3.orig/Makefile popa3d-1.0.3/Makefile
--- popa3d-1.0.3.orig/Makefile	2006-03-05 05:36:54.000000000 -0500
+++ popa3d-1.0.3/Makefile	2024-05-15 16:04:45.441343266 -0400
@@ -3,28 +3,28 @@
 RM = rm -f
 MKDIR = mkdir -p
 INSTALL = install -c
-CFLAGS = -Wall -O2 -fomit-frame-pointer
+CFLAGS = -pipe -O2 -fomit-frame-pointer
 # You may use OpenSSL's MD5 routines instead of the ones supplied here
 #CFLAGS += -DHAVE_OPENSSL
 LDFLAGS = -s
 LIBS =
 # Linux with glibc, FreeBSD, NetBSD
-#LIBS += -lcrypt
+LIBS += -lcrypt
 # HP-UX trusted system
 #LIBS += -lsec
 # Solaris (POP_STANDALONE, POP_VIRTUAL)
 #LIBS += -lsocket -lnsl
 # PAM
-#LIBS += -lpam
+LIBS += -lpam
 # TCP wrappers
 #LIBS += -lwrap
 # libwrap may also want this
 #LIBS += -lnsl
 # OpenSSL (-DHAVE_OPENSSL)
-#LIBS += -lcrypto
+LIBS += -lcrypto
 
 DESTDIR =
-PREFIX = /usr/local
+PREFIX = /usr
 SBINDIR = $(PREFIX)/sbin
 MANDIR = $(PREFIX)/man
 
diff -Nur popa3d-1.0.3.orig/params.h popa3d-1.0.3/params.h
--- popa3d-1.0.3.orig/params.h	2006-03-05 08:18:32.000000000 -0500
+++ popa3d-1.0.3/params.h	2024-05-15 16:06:37.097555265 -0400
@@ -103,7 +103,7 @@
  * A pseudo-user to run as before authentication.  The user and its UID
  * must not be used for any other purpose.
  */
-#define POP_USER			POP_SERVER
+#define POP_USER			"pop"
 
 /*
  * An empty directory to chroot to before authentication.  The directory
@@ -155,8 +155,8 @@
  * Note that there's no built-in password aging support.
  */
 #define AUTH_PASSWD			0
-#define AUTH_SHADOW			1
-#define AUTH_PAM			0
+#define AUTH_SHADOW			0
+#define AUTH_PAM			1
 #define AUTH_PAM_USERPASS		0
 #define USE_LIBPAM_USERPASS		0
 
@@ -191,7 +191,7 @@
  *
  * #undef this for qmail-style $HOME/Mailbox mailboxes.
  */
-#define MAIL_SPOOL_PATH			"/var/mail"
+#define MAIL_SPOOL_PATH			"/var/spool/mail"
 
 #ifndef MAIL_SPOOL_PATH
 /*

> telnet 192.168.20.1 110
Trying 192.168.20.1...
Connected to 192.168.20.1.
Escape character is '^]'.
+OK
USER jayjwa
+OK
PASS s3cr3t
+OK
STAT
+OK 9 159760
QUIT
+OK
Connection closed by foreign host.