Package: clamsmtp

"clamsmtp" package binaries on CentOS:

/usr/sbin/clamd.clamsmtp /usr/sbin/clamsmtpd

You may install this package on CentOS with yum install clamsmtp

"clamsmtp" package binaries on Debian:

/usr/sbin/clamsmtpd

You may install this package on Debian with apt-get install clamsmtp