Since I configured my mail server, I was getting the following lines in my auth.log.  Everything was working, users had to log in to receive or send mail, so the messages were really cluttering the logfile.

Nov 28 00:02:39 rm-003-11 lmtpunix[1085]: sql_select option missing
Nov 28 00:02:39 rm-003-11 lmtpunix[1085]: auxpropfunc error no mechanism available
Nov 28 00:05:44 rm-003-11 postfix/smtpd[1106]: sql_select option missing
Nov 28 00:05:44 rm-003-11 postfix/smtpd[1106]: auxpropfunc error no mechanism available
Nov 28 00:06:08 rm-003-11 postfix/smtpd[1108]: sql_select option missing

I wasn\'t using auxprop as the method to check passwords, I am using saslauth.  But googling around to find a way to get rid of them did not find a solution.  On a hunch, I uninstalled the libsasl2-modules-sql package for my Debian version, and the lines have stopped showing up in the authentication logfile.  Everything is still working, so that package wasn\'t needed by my setup.