When trying to run Postfix with virtual maps in MySQL, you can get the following error:

connect to mysql server localhost: Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' postfix

This error is because postfix is running in chroot /var/spool/postfix. So it cannot find the unix socket for MySQL.

If you have the option to run mysql on 127.0.0.1 or on another IP, simply go to;

/etc/postfix

run;

grep localhost *

and replace all localhost to 127.0.0.1 or the IP in all files starting with mysql-virtual.

If you insist on running via unix sockets, you can simply fix it by running;

mkdir /var/spool/postfix/var
mount –bind /var /var/spool/postfix/var

Ater this, all will work fine.