If you are running CentOS, you are most probably already have sendmail MTA, so you can send mails via PHP if that is what you are really after. Sending and receiving will be a different story.
For SQL server, that depends on which particular SQL server you want MySQL/PostgreSQL/Oracle? To check if they are installed just use the command:
Code:
yum list installed|grep sql
You should come up with a list like:
Code:
[root@zeus ~]# yum list installed|grep sql
mysql.i386 5.0.79-1.el5.art installed
mysql-devel.i386 5.0.79-1.el5.art installed
mysql-libs.i386 5.0.79-1.el5.art installed
mysql-server.i386 5.0.79-1.el5.art installed
perl-DBD-mysql.i386 4.010-1.el5.rf installed
php-mysql.i386 5.2.9-2.el5.art installed
postgresql-libs.i386 8.1.11-1.el5_1.1 installed
python-sqlite.i386 1.1.7-1.2.1 installed
sqlite.i386 3.3.6-2 installed
sqlite-devel.i386 3.3.6-2 installed
As you can see from my result, MySQL server is installed as well as the corresponding PHP extension, php-mysql.
HTH