Using smbclient with an auth file (-A) and valid logins to a domain is resulting in LOGIN_FAILED for all but one system (Win 2k12 server.) However if I use the same credentials with a -U flag I am able to log into the systems without issue. I also tested v3.6.19 with the same auth file against the same systems and had no issues whatsoever. I downloaded and compiled the source from the samba.org website. This also appears to affect v4.0.9 and v4.1.0 (No other v4 were tested.) Build: cd samba/source3 ./autogen.sh ./configure make -j8 no errors during build. I copy the smbclient bin to the home directory and run it. I do receive an error about the smb.conf but I am not concerned with that since it doesn't appear to affect using the binary with the -U option so I assume it should work with the -A option and a properly formatted auth file. Authfile - Domain User: username=topdog password=P@ssW0rd domain=brav0hax The authfile above does not work however the auth file below works without issue: Auth file - Local User: username=administrator password=Ihazpassword! domain=. Systems connecting to: Windows 2012 Server 64-Bit Windows 2008 Server 64-Bit Windows 2003 Server 32-Bit Windows 8 64 bit Windows 7 32-Bit Windows XP 32-Bit Command used: ./smbclient -A test //IP/C$ (Only works agains the Win2k12 set up as the DC) ./smbclient -U brav0hax/topdog%P@ssW0rd //IP/C$ (Works with all systems without issue) ldd info (smbclient 4.0.10): root:~/Downloads# ldd ./smbclient linux-gate.so.1 => (0xb7736000) libreadline.so.6 => /lib/i386-linux-gnu/libreadline.so.6 (0xb6dfe000) libtinfo.so.5 => /lib/i386-linux-gnu/libtinfo.so.5 (0xb6dde000) libresolv.so.2 => /lib/i386-linux-gnu/i686/cmov/libresolv.so.2 (0xb6dc9000) libnsl.so.1 => /lib/i386-linux-gnu/i686/cmov/libnsl.so.1 (0xb6db2000) libdl.so.2 => /lib/i386-linux-gnu/i686/cmov/libdl.so.2 (0xb6dae000) librt.so.1 => /lib/i386-linux-gnu/i686/cmov/librt.so.1 (0xb6da5000) libpthread.so.0 => /lib/i386-linux-gnu/i686/cmov/libpthread.so.0 (0xb6d8c000) libpopt.so.0 => /lib/i386-linux-gnu/libpopt.so.0 (0xb6d7e000) libgssapi_krb5.so.2 => /usr/lib/i386-linux-gnu/libgssapi_krb5.so.2 (0xb6d40000) libkrb5.so.3 => /usr/lib/i386-linux-gnu/libkrb5.so.3 (0xb6c6e000) libk5crypto.so.3 => /usr/lib/i386-linux-gnu/libk5crypto.so.3 (0xb6c44000) libcom_err.so.2 => /lib/i386-linux-gnu/libcom_err.so.2 (0xb6c3f000) libldap_r-2.4.so.2 => /usr/lib/i386-linux-gnu/libldap_r-2.4.so.2 (0xb6bec000) liblber-2.4.so.2 => /usr/lib/i386-linux-gnu/liblber-2.4.so.2 (0xb6bdd000) libtalloc.so.2 => /usr/lib/i386-linux-gnu/libtalloc.so.2 (0xb6bd1000) libtevent.so.0 => /usr/lib/i386-linux-gnu/libtevent.so.0 (0xb6bc3000) libwbclient.so.0 => /usr/lib/i386-linux-gnu/libwbclient.so.0 (0xb6bb5000) libz.so.1 => /lib/i386-linux-gnu/libz.so.1 (0xb6b9b000) libc.so.6 => /lib/i386-linux-gnu/i686/cmov/libc.so.6 (0xb6a38000) /lib/ld-linux.so.2 (0xb7737000) libkrb5support.so.0 => /usr/lib/i386-linux-gnu/libkrb5support.so.0 (0xb6a2f000) libkeyutils.so.1 => /lib/i386-linux-gnu/libkeyutils.so.1 (0xb6a2a000) libsasl2.so.2 => /usr/lib/i386-linux-gnu/libsasl2.so.2 (0xb6a0e000) libgnutls.so.26 => /usr/lib/i386-linux-gnu/libgnutls.so.26 (0xb6944000) libgcrypt.so.11 => /lib/i386-linux-gnu/libgcrypt.so.11 (0xb68bf000) libwinbind-client.so => /usr/lib/i386-linux-gnu/samba/libwinbind-client.so (0xb68bb000) libbsd.so.0 => /lib/i386-linux-gnu/libbsd.so.0 (0xb68ad000) libtasn1.so.3 => /usr/lib/i386-linux-gnu/libtasn1.so.3 (0xb689a000) libp11-kit.so.0 => /usr/lib/i386-linux-gnu/libp11-kit.so.0 (0xb6888000) libgpg-error.so.0 => /lib/i386-linux-gnu/libgpg-error.so.0 (0xb6884000)