Disable SMB Signing on MAC OS Sierra

 sudo -s
 echo "[default]" > /etc/nsmb.conf
 echo signing_required=no >> /etc/nsmb.conf
 exit

To check that it properly wrote the nsmb.conf file:

 cat /etc/nsmb.conf

result:

 [default]
signing_required=no

Check if SMB signing is disabled on your share after you remount the SMB volume smbutil statshares -a

==================================================================================================
SHARE ATTRIBUTE TYPE VALUE
==================================================================================================

If you see the the SIGNING_ON = TRUE Variable, that means its still on and you did not execute the instructions properly.

This variable should not show up after you have disabled SMB signing on the OS X 10.11.5 client. This is also applicable for OS X 10.11.6>10.12 (Mac OS Sierra)