I have checked this site. and i found this(check below). it says qmail not "Qmail". i think there is some differences between this two?
1.2. What is qmail?
qmail is an Internet Mail Transfer Agent (MTA) for UNIX-like operating
systems. It's a drop-in replacement for the Sendmail system provided
with UNIX operating systems. qmail uses the Simple Mail Transfer
Protocol (SMTP) to exchange messages with MTA's on other systems.
Note: The name is "qmail", not "Qmail".