Qmail Interview Questions & Answers part 4


Q: – Tell me the name of five Important Qmail daemons?


Q: – How to rebuild the SMTP access database?

qmailctl cdb
tcprules /etc/tcp.smtp.cdb /etc/tcp.smtp.tmp < /etc/tcp.smtp
chmod 644 /etc/tcp.smtp*

Q: – Which mailing list you have configured with qmail?


Q: – Explain the working of qmail?

For mail arriving from remote systems, tcpserver runs as a daemon listening for incoming connections on the SMTP port. Each time a connection arrives, it runs qmail-smtpd, which receives a message via SMTP and calls qmail-queue to queue the message. Regardless of where the message originates, qmail-queue writes the message to a temporary file in the queue/todo directory, putting a new Received: line at the top, and also saves the envelope sender and recipient addresses to files. Then it notifies qmail-send by writing a byte to a "trigger" socket file. qmail-send takes the message out of queue/todo, and analyzes each recipient address to see if it's local, remote, or virtual. For local addresses, it notifies qmail-lspawn to run qmail-local to do the local deliveries. For each remote address, qmail-send notifies qmail-rspawn to run qmail-remote to do the remote deliveries. For virtual addresses, qmail-send rewrites each virtual address as a modified local address, using the information from the virtualdomains files.

Q: – What is the use of “queuelifetime” qmail control file?

This qmail control file is used by qmail-send daemon. In this file we define how long to keep trying to deliver a message. The default value is 604800 seconds (a week).

Q: – What is the use of “timeoutconnect” qmail control file?

This qmail control file is used by qmail-remote daemon. In this file we define how long to wait for a remote server to accept the initial connection to send mail. The default value is 60 seconds.

Q: –What is the use of “virtualdomains” qmail control file?

The list of virtual users and domains for which this system receives mail. The default value in this file is none.

Q: – Have you installed autoresponder & what is the use of autoresponder?

Yes, this is a simple program to automatically respond to emails.

Q: – What is “ucspi-tcp”?

A package for servers that respond to incoming TCP connections, as an alternative to the old inetd daemon. It used to be optional, but its tcpserver is now the only supported way to run qmail's SMTP daemon.

Submitted By:-Payal Chauhan            Email-ID: – payalchauhan@ibibo.com