Mail Server Interview Questions & Answers

  1. Question 1. What Is A Postfix Mail Server?

    Answer :

    A mail server is an application that receives incoming e-mail from local users and forwards outgoing e-mail for delivery. A computer dedicated to running such applications is called a Mail Server.

  2. Question 2. What Is The Location Of Postfix Mail Server Queue?

    Answer :

    By default, the Postfix mail queues are located in the /var/spool/postfix directory.

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  4. Question 3. What Is Postfix And Default Port Used For Postfix?

    Answer :

    Postfix is an open source MTA (Mail Transfer agent) which is used to route & deliver emails. Default port for postfix is 25.

  5. Question 4. What Is Smtp And Its Default Port?

    Answer :

    SMTP is part of the application layer. SMTP moves your email across the networks. SMTP by default uses TCP port no 25. It also uses port no 587 for connections secured by SSL, known as SMTPS.

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  7. Question 5. What Is Dovecot?

    Answer :

    Dovecot is an open-source IMAP and POP3 server for Linux/UNIX-like systems, written primarily with security in mind.

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  9. Question 6. What Is Mta And Its Role In Mailing System?

    Answer :

    A message transfer agent (MTA) is a software application used within an Internet message handling system. It is responsible for transferring and routing an email messages from the sender’s computer to the recipient’s computer.

  10. Question 7. What Is Mda?

    Answer :

    MDA stands for Mail Delivery Agent. MDA is a Program that handles final delivery of messages for a system’s local recipients.

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  12. Question 8. What Is Mua?

    Answer :

    MUA stands for Mail User Agent. MUA is an Email client software used to compose, send, and receive email messages. It sends messages through an MTA. Retrieves messages from a mail store either directly or through a POP/ IMAP server. Examples Outlook and Thunderbird.

  13. Question 9. How To Check Version Of Postfix?

    Answer :

    # postconf –d | grep mail_version

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  15. Question 10. Tell Me About Latest Version Of Postfix On Which U Have Worked?

    Answer :

    postfix 2.6

  16. Question 11. What Is The Use Of Postmaster Account In Mail Server?

    Answer :

    • An email administrator is commonly referred to as a postmaster. 
    • Postmaster Mail Server lets you send and receive email from any desktop on LAN. There is no need for a modem with every computer. 
    • It allows you to allot individual email ids like person@company.com to every executive.
    • Postmaster supports multiple domains. You can send/receive emails from all the domains that your organization uses.
    • Postmaster works as a low cost SMTP Gateway.
    • You can set different schedules for different days of the week for automatic dial-up and mail transfer. Thus you can check mail more frequently on busy days, automatically.
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  18. Question 12. What Are The Configuration Files Of Postfix Server?

    Answer :

    There are two main Configuration files of postfix: 

    1. /etc/postfix/main.cf
    2. /etc/postfix/master.cf
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  20. Question 13. How To Check The Mail’s Queue In Postfix?

    Answer :

    To display the list of queued mails: 
    # postqueue -p
    To Save the output of above command: 
    # postqueue -p > /mnt/queue-backup.txt
    Tell Postfix to process the Queue now: 
    # postqueue -f

  21. Question 14. How To Delete Mails From The Queue In Postfix? Or How Can I Clear Postfix Mail Server Queue?

    Answer :

    # postsuper -d ALL

  22. Question 15. How You Will Reload The Postfix Queue?

    Answer :

    # postsuper -r ALL

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  24. Question 16. How To Check Postfix Configuration From The Command Line?

    Answer :

    psotconf -n

  25. Question 17. Which Command Is Used To See Live Mail Logs In Postfix?

    Answer :

    # tail -f /var/log/maillog OR 

    tailf /var/log/maillog

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  27. Question 18. How To Send A Test Mail From Command Line?

    Answer :

    # echo “Test mail from postfix” | mail -s “Plz ignore” user@company.com

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  29. Question 19. What Is An Open Mail Relay?

    Answer :

    An open mail relay is an SMTP server configured in such a way that it allows anyone on the Internet to send e-mail through it, not just mail destined to or originating from known users.This used to be the default configuration in many mail servers. It was the way the Internet was initially set up, but open mail relays have become unpopular because of their exploitation by spammers and worms.

  30. Question 20. Which Command Is Used To Find Out That Postfix Is Complied With Mysql Or Not?

    Answer :

    # postconf -m

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  32. Question 21. What Is Spamassassin?

    Answer :

    SpamAssassin is a mail filter to identify spam. It is an intelligent email filter which uses a diverse range of tests to identify unsolicited bulk email, more commonly known as Spam. These tests are applied to email headers and content to classify email using advanced statistical methods.

  33. Question 22. If You Have 40000 Mail In Queue Of Your Mail Server How Will You Troubleshoot Step By Step?

    Answer :

    Depends on what mails are there whether important mail or not important (delete not important mails and for important email re-queue postfix to send mail again). 

  34. Question 23. You Mail Server Is Working Properly Still Your Users Are Not Getting Mail How Will You Troubleshoot?

    Answer :

    Check log (eg /var/log/maillog) and try to find the error

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  36. Question 24. If Reverse Dns Entry For Your Mail Server Is Wrong Which Error You Will Get And How It Will Effect Your Mail Server?

    Answer :

    Server refused to talk to me: 550 Reverse DNS lookup failed for host XX.XXX. (port 25)

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  38. Question 25. Describe Below Mentioned Postfix Support Commands?

    Answer :

    • The postfix: command controls the operation of the mail system. It is the interface for starting, stopping, and restarting the mail system. This command is reserved to the super-user.
    • The postalias: command maintains Postfix aliases type databases. This is the program that does the work for the newaliases command.
    • The postcat: command displays the contents of Postfix queue files. This is a limited, preliminary utility. This program is likely to be superseded by something more powerful that can also edit Postfix queue files.
    • The postconf: command displays or updates Postfix main.cf parameters and displays system dependent information about the supported file locking methods, and the supported types of lookup tables.
    • The postdrop: command is the mail posting utility that is run by the Postfix sendmail command in order to deposit mail into the maildrop queue directory.
    • The postkick: command makes some Postfix internal communication channels available for use in, for example, shell scripts.
    • The postlock: command provides Postfix-compatible mailbox locking for use in, for example, shell scripts.
    • The postlog: command provides Postfix-compatible logging for shell scripts.
    • The postmap: command maintains Postfix lookup tables such as canonical, virtual and others. It is a cousin of the UNIX makemap command.
    • The postmulti: command repeats the “postfix start” etc. command for each Postfix instance, and supports creation, deletion etc. of Postfix instances. For a tutorial, see MULTI_INSTANCE_README.
    • The postqueue: command is the privileged command that is run by Postfix sendmail and mailq in order to flush or list the mail queue.
    • The postsuper: command maintains the Postfix queue. It removes old temporary files, and moves queue files into the right directory after a change in the hashing depth of queue directories. This command is run at mail system startup time and when Postfix is restarted.
  39. Question 26. If Your Mail Server Is Working Properly But When You Are Trying To Send Mail For Hotmail It Is Showing Error Relay Access Denied How Will You Troubleshoot?

    Answer :

    check for the proper relay or postifx main.cf file for the relay address.

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  41. Question 27. What Is Canonical Table?

    Answer :

    A canonical object means an object with a single reference pointed to it, with no copies holding the same state possible. The activity of replacing multiple copies of an object with just a few objects is often referred to as canonicalizing objects.

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