dspam_merge: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/dspam_merge - from package: dspam

You may install the required package with command yum install {package}
Error in other languages:
dspam_merge: bevel nie gevind nie
dspam_merge: comandă negăsită
dspam_merge: comando não encontrado
dspam_merge: commande introuvable
dspam_merge: command not found
dspam_merge: käsku ei ole
dspam_merge: không tìm thấy lệnh
dspam_merge: komanda nerasta
dspam_merge: Kommando nicht gefunden.
dspam_merge: kommandot finns inte
dspam_merge: komut yok
dspam_merge: nie znaleziono polecenia
dspam_merge: níor aimsíodh an t-ordú
dspam_merge: no se encontró la orden
dspam_merge: no s'ha trobat l'ordre
dspam_merge: opdracht niet gevonden
dspam_merge: parancs nem található
dspam_merge: perintah tidak ditemukan
dspam_merge: príkaz nenájdený
dspam_merge: příkaz nenalezen
dspam_merge: команда не найдена
dspam_merge: командата не е открита
dspam_merge: 命令找不到
dspam_merge: コマンドが見つかりません