Dovecot fails to compile against PostgreSQL 9.2

If you are trying to compile dovecot against PostgreSQL, then you are probably running configure with the "--with-pgsql" option.  Except that if you installed PostgreSQL via the PGDG repository on Centos 6, you are probably stuck with the following error:

checking for shadow.h... yes
checking for pam_start in -lpam... no
checking for auth_userokay... no
checking for pg_config... NO
checking for PQconnectdb in -lpq... no
configure: error: Can't build with PostgreSQL support: libpq not found

The root cause is that pg_config is not in the PATH statement.  So you should add "/usr/pgsql-9.2/bin" to your PATH statement before calling ./configure.  If you are not sure where pg_config is located, try "find / -name pg_config".

#!/bin/bash
PATH=/usr/pgsql-9.2/bin:$PATH
export PATH
./configure \
        --with-pgsql

Once you do the above, the dovecot 2.2 configure script will run to completion.