Interview Questions.

Question 1. What Is Postfix And Default Port Used For Postfix ?

Answer :

Postfix is a open source MTA (Mail Transfer agent) which is used to route & deliver emails. Postfix is the alternate of extensively used Sendmail MTA. Default port for postfix is 25.

Question 2. What Is The Difference Between Postfix & Sendmail ?

Answer :

Postfix uses a modular method and consists of more than one independent executables. Sendmail has a extra monolithic design utilizing a unmarried constantly strolling daemon.

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Question three. What Is Mta And It’s Role In Mailing System ?

Answer :

MTA Stands for Mail Transfer Agent.MTA receives and delivers e mail. Determines message routing and possible cope with rewriting. Locally brought  messages are exceeded off to an MDA for final delivery. Examples Qmail, Postfix, Sendmail.

Question 4. What Is Mda ?

Answer :

MDA stands for Mail Delivery Agent. MDA is a Program that handles very last delivery of messages for a machine’s neighborhood recipients. MDAs can often filter or categorize messages upon shipping. An MDA may additionally determine that a message ought to be forwarded to any other email deal with. Example Procmail.

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Question 5. What Is Mua ?

Answer :

MUA stands for Mail User Agent. MUA is a Email purchaser software program used to compose, ship, and retrieve email messages. Sends messages thru an MTA. Retrieves messages from a mail keep either at once or through a POP/ IMAP server. Examples Outlook, Thunderbird, Evolution.

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Question 6. What Is The Use Of Postmaster Account In Mailserver ?

Answer :

An e-mail administrator is commonly known as a postmaster. An individual with postmaster responsibilities makes certain that the mail system is running successfully, makes configuration adjustments, and provides/removes e mail money owed, amongst different matters. You should have a postmaster alias at all domains for which you take care of email that directs messages to the proper individual or folks .

Question 7. What Are The Important Daemons In Postfix ?

Answer :

 

Below are the lists of vital daemon in postfix mail server :

master :The master daemon is the mind of the Postfix mail machine. It spawns all different daemons.
Smtpd: The smtpd daemon (server) handles incoming connections.
Smtp :The smtp customer handles outgoing connections.
Qmgr :The qmgr-Daemon is the coronary heart of the Postfix mail machine. It tactics and controls all messages inside the mail queues.
Neighborhood : The local application is Postfix’ very own nearby transport agent. It shops messages in mailboxes.
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Question 8. What Are The Configuration Files Of Postfix Server ?

Answer :

There are  foremost Configuration files of postfix :

/etc/postfix/main.Cf : This record holds international configuration options. They could be implemented to all times of a daemon, except they are overridden in grasp.Cf
/and so on/postfix/master.Cf  : This document defines runtime surroundings for daemons attached to services. Runtime conduct described in foremost.Cf can be overridden by way of putting provider precise options.
Question 9. How To Restart The Postfix Service & Make It Enable Across Reboot ?

Answer :

Use this command to restart service “ Service postfix restart” and to make the carrier persist throughout the reboot, use the command “ chkconfig postfix on”.

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Question 10. How To Check The Mail’s Queue In Postfix ?

Answer :

Postfix maintains  queues, the pending mails queue, and the deferred mail queue,the deferred mail queue has the mail that has gentle-fail and should be retried (Temporary failure), Postfix retries the deferred queue on set intervals (configurable, and by using default 5 minutes)

To display the listing of queued mails :

# postqueue -p
To Save the output of above command :
# postqueue -p > /mnt/queue-backup.Txt
Tell Postfix to procedure the Queue now
# postqueue -f

Question eleven. How To Delete Mails From The Queue In Postfix ?

Answer :

Use below command to delete all queued mails

# postsuper -d ALL

To delete simplest deferred mails from queue , use underneath command

# postsuper -d ALL deferred

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Question 12. How To Check Postfix Configuration From The Command Line ?

Answer :

Using the command ‘postconf -n‘  we are able to see modern-day configuration of postfix excluding the lines which might be commented.

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Question thirteen. Which Command Is Used To See Live Mail Logs In Postfix ?

Answer :

Use the command  ‘tail -f /var/log/maillog’ or ‘tailf /var/log/maillog’.

Question 14. How To Send A Test Mail From Command Line ?

Answer :

Use the below command to ship a test mail -s “Plz ignore” info@something.Com

Question 15. What Is An Open Mail Relay ?

Answer :

An open mail relay is an SMTP server configured in this sort of manner that it lets in all people on the Internet to send e-mail through it, now not just mail destined to or originating from known users.This was the default configuration in many mail servers; indeed, it became the manner the Internet was to begin with installation, however open mail relays have end up unpopular due to their exploitation via spammers and worms.

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Question 16. What Is Relay Host In Postfix ?

Answer :

Relay host is the smtp cope with , if cited in postfix config file , then all the incoming mails be relayed through smtp server.

Question 17. What Is Greylisting ?

Answer :

Greylisting is a way of defending electronic mail customers towards junk mail. A mail switch agent (MTA) the use of greylisting will “briefly reject” any email from a sender it does not understand. If the mail is valid the originating server will, after a put off, strive once more and, if sufficient time has elapsed, the email might be normal.

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Question 18. What Is The Importance Of Spf Records In Mail Servers ?

Answer :

SPF (Sender Policy Framework) is a gadget to assist domain proprietors specify the servers which are presupposed to ship mail from their domain. The goal is that other mail systems can then take a look at to ensure the server sending electronic mail from that area is authorized to achieve this – reducing the threat of e mail ‘spoofing’, phishing schemes and spam!

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Question 19. What Is The Use Of Domain Keys(dkim) In Mail Servers ?

Answer :

DomainKeys is an electronic mail authentication gadget designed to confirm the DNS area of an email sender and the message integrity. The DomainKeys specification has followed elements of Identified Internet Mail to create an superior protocol called DomainKeys Identified Mail (DKIM).

Question 20. What Is The Role Of Anti-spam Smtp Proxy (assp) In Mail Server ?

Answer :

ASSP is a gateway server that's deploy in the front of your MTA and implements vehicle-whitelists, self learning Bayesian, Greylisting, DNSBL, DNSWL, URIBL, SPF, SRS, Backscatter, Virus scanning, attachment blocking, Senderbase and a couple of different clear out techniques.

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