pam_mysql - something went wrong when invoking crypt()
 

I have this error to authenticate the postfix + mysql...


You are missing some library ?

Read the Question Guidelines link in my posting signature. When you don't provide any useful details, there is no way anyone can help you. You don't say what version/distro of Linux you're using, version of postfix, MySQL, what you've done/tried, etc. What, exactly, do you think we'll be able to tell you???

ubuntu server 14.04

root@protus:/etc/postfix/sasl# dpkg --list | grep mysql
ii libdbd-mysql-perl 4.025-1 amd64 Perl5 database interface to the MySQL database
ii libmysqlclient18:amd64 5.5.47-0ubuntu0.14.04.1 amd64 MySQL database client library
ii libpam-mysql 0.7~RC1-4ubuntu1 amd64 PAM module allowing authentication from a MySQL server
ii mysql-client-5.5 5.5.47-0ubuntu0.14.04.1 amd64 MySQL database client binaries
ii mysql-client-core-5.5 5.5.47-0ubuntu0.14.04.1 amd64 MySQL database core client binaries
ii mysql-common 5.5.47-0ubuntu0.14.04.1 all MySQL database common files, e.g. /etc/mysql/my.cnf
ii mysql-server 5.5.47-0ubuntu0.14.04.1 all MySQL database server (metapackage depending on the latest version)
ii mysql-server-5.5 5.5.47-0ubuntu0.14.04.1 amd64 MySQL database server binaries and system database setup
ii mysql-server-core-5.5 5.5.47-0ubuntu0.14.04.1 amd64 MySQL database server binaries
ii php5-mysql 5.5.9+dfsg-1ubuntu4.14 amd64 MySQL module for php5
ii postfix-mysql 2.11.0-1ubuntu1 amd64 MySQL map support for Postfix


root@protus:/etc/postfix/sasl# dpkg --list | grep libpam
ii libpam-cap:amd64 1:2.24-0ubuntu2 amd64 PAM module for implementing capabilities
ii libpam-modules:amd64 1.1.8-1ubuntu2.2 amd64 Pluggable Authentication Modules for PAM
ii libpam-modules-bin 1.1.8-1ubuntu2.2 amd64 Pluggable Authentication Modules for PAM - helper binaries
ii libpam-mysql 0.7~RC1-4ubuntu1 amd64 PAM module allowing authentication from a MySQL server
ii libpam-runtime 1.1.8-1ubuntu2.2 all Runtime support for the PAM library
ii libpam-systemd:amd64 204-5ubuntu20.18 amd64 system and service manager - PAM module
ii libpam0g:amd64 1.1.8-1ubuntu2.2 amd64 Pluggable Authentication Modules library
ii libpam0g-dev:amd64 1.1.8-1ubuntu2.2 amd64 Development files for PAM

Great...so now again, what have you done/tried???? What instructions/guides have you attempted to follow, and what is the WHOLE error message (say, including the file name in question??)

i using ubuntu 14.04 server...

The error occurs when sending an authenticated email. ( Postfix + saslauthd )

in /var/log/auth

Right, which you said after you had to be asked.
..and we're back to "What guides did you follow, what have you done/tried??? What is the ENTIRE ERROR MESSAGE??????

If you're not going to provide details, there is no point in posting. We aren't going to play guessing games, trying to help you solve your problem.