**Postfix interview questions and answers**

Table of Contents

1) What Is Postfix And Default Port Used For Postfix ?

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.

2) What Is The Difference Between Postfix & Sendmail ?

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.

3) What Is Mta And It’s Role In Mailing System ?

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.

4) What Is Mda ?

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.

5) What Is Mua ?

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.

6) What Is The Use Of Postmaster Account In Mailserver ?

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 .

7) What Are The Important Daemons In Postfix ?

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.

8) What Are The Configuration Files Of Postfix Server ?

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.

9) How To Restart The Postfix Service & Make It Enable Across Reboot ?

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

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

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

11) How To Delete Mails From The Queue In Postfix ?

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

12) How To Check Postfix Configuration From The Command Line ?

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

13) Which Command Is Used To See Live Mail Logs In Postfix ?

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

14) How To Send A Test Mail From Command Line ?

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

15) What Is An Open Mail Relay ?

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.

16) What Is Postfix And Default Port Used For Postfix ?

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

17) What Is The Difference Between Postfix & Sendmail ?

Postfix uses a modular approach and is composed of multiple independent executables. Sendmail has a more monolithic design utilizing a single always running daemon.

18) What Is Mta And It’s Role In Mailing System ?

MTA Stands for Mail Transfer Agent.MTA receives and delivers email. Determines message routing and possible address rewriting. Locally delivered messages are handed off to an MDA for final delivery. Examples Qmail, Postfix, Sendmail.

19) What Are The Important Daemons In Postfix ?

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

master :The master daemon is the brain of the Postfix mail system. It spawns all other daemons.
smtpd: The smtpd daemon (server) handles incoming connections.
smtp :The smtp client handles outgoing connections.
qmgr :The qmgr-Daemon is the heart of the Postfix mail system. It processes and controls all messages in the mail queues.
local : The local program is Postfix’ own local delivery agent. It stores messages in mailboxes.

20) How To Check Postfix Configuration From The Command Line ?

Using the command ‘postconf -n‘ we can see current configuration of postfix excluding the lines which are commented.

21) What Is An Open Mail Relay ?

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; indeed, 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.

22) What Is Greylisting ?

Greylisting is a method of defending e-mail users against spam. A mail transfer agent (MTA) using greylisting will “temporarily reject” any email from a sender it does not recognize. If the mail is legitimate the originating server will, after a delay, try again and, if sufficient time has elapsed, the email will be accepted.

23) What Is The Importance Of Spf Records In Mail Servers ?

SPF (Sender Policy Framework) is a system to help domain owners specify the servers which are supposed to send mail from their domain. The aim is that other mail systems can then check to make sure the server sending email from that domain is authorized to do so – reducing the chance of email ‘spoofing’, phishing schemes and spam!

24) What Is The Use Of Domain Keys(dkim) In Mail Servers ?

DomainKeys is an e-mail authentication system designed to verify the DNS domain of an e-mail sender and the message integrity. The DomainKeys specification has adopted aspects of Identified Internet Mail to create an enhanced protocol called DomainKeys Identified Mail (DKIM).

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

ASSP is a gateway server which is install in front of your MTA and implements auto-whitelists, self learning Bayesian, Greylisting, DNSBL, DNSWL, URIBL, SPF, SRS, Backscatter, Virus scanning, attachment blocking, Senderbase and multiple other filter methods

26) How to check postfix configuration from the command line ?

Using the command ‘postconf -n‘ we can see current configuration of postfix excluding the lines which are commented.

27) Which command is used to see live mail logs in postfix ?

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

28) What is an Open mail relay ?

29) What is the use of Domain Keys(DKIM) in mail servers ?

30) What is the role of Anti-Spam SMTP Proxy (ASSP) in mail server ?

31) Who makes Postfix?

Postfix (software)

Original author(s)	Wietse Venema at the IBM Thomas J. Watson Research Center
Developer(s)	Venema and many others
Initial release	December 14, 1998
Stable release	3.7.0 / 5 February 2022
Preview release	3.8-20220325 / March 25, 2022

32) What protocol does Postfix use?

SMTP protocol
As the MTA, Postfix receives and delivers email messages over the network via the SMTP protocol.

33) What language is Postfix?

Post- fix is a simple stack-based language inspired by the PostScript graphics language, the Forth programming language, Hewlett Packard calculators, and stack-based bytecode interpreters. Here we give a brief introduction to Postfix. The basic syntactic unit of a Postfix program is the command.

34) What is a postfix example?

For example, the infix expression (2+3)(4+5) in postfix notation is 23+45+ and the infix expression 2+34+5 in postfix notation is 234+5+. Also, since our four operators are left associative, 2 + 3 + 4 translates to 23+4+ and not 234++.

35) Where is Postfix config?

/etc/postfix
By default, Postfix configuration files are in /etc/postfix. The two most important files are main.cf and master.cf; these files must be owned by root.

36) What is Postfix SMTP?

Postfix is a mail transfer agent (MTA), an application used to send and receive email. In this tutorial, we will install and configure Postfix so that it can be used to send emails by local applications only — that is, those installed on the same server that Postfix is installed on.

37) Does postfix use SSL?

Postfix should now support incoming connections using SSL, meaning that your emails should now be encrypted and secure during transmission to your client.

38) Does postfix use OpenSSL?

Starting with Postfix 2.11, linked with a compatible OpenSSL library (at least 0.9. 8h, preferably 1.0. 0 or later) the Postfix SMTP server supports RFC 5077 TLS session resumption without server-side state when the remote SMTP client also supports RFC 5077.

39) Why is OpenSSL needed?

Why do you need OpenSSL? With OpenSSL, you can apply for your digital certificate (Generate the Certificate Signing Request) and install the SSL files on your server. You can also convert your certificate into various SSL formats, as well as do all kind of verifications

40) What is HTTPS and TLS?

It is used for secure communication over a computer network, and is widely used on the Internet. In HTTPS, the communication protocol is encrypted using Transport Layer Security (TLS) or, formerly, Secure Sockets Layer (SSL). The protocol is therefore also referred to as HTTP over TLS, or HTTP over SSL.

41) How does TLS security work?

TLS Basics. Transport Layer Security (TLS) encrypts data sent over the Internet to ensure that eavesdroppers and hackers are unable to see what you transmit which is particularly useful for private and sensitive information such as passwords, credit card numbers, and personal correspondence.

42) What uses TLS?

Both TLS and SSL are widely used in web browsers, email, messaging apps, and other applications—although TLS has generally displaced SSL in newer systems. Generally, TLS offers stronger encryption algorithms for authentication and supports pre-shared keys and secure remote passwords.

43) What is HTTP handshake?

In telecommunications, a handshake is an automated process of negotiation between two participants (example “Alice and Bob”) through the exchange of information that establishes the protocols of a communication link at the start of the communication, before full communication begins.

44) What port does SSL use?

port 443
HTTPS traffic uses port 443, which is why it’s sometimes referred to as SSL certificate port 443.

45) How does HTTPS work step by step?

HTTPS occurs based upon the transmission of TLS/SSL certificates, which verify that a particular provider is who they say they are. When a user connects to a webpage, the webpage will send over its SSL certificate which contains the public key necessary to start the secure session.

46) Are HTTP websites safe?

HTTPS is HTTP with encryption. The only difference between the two protocols is that HTTPS uses TLS (SSL) to encrypt normal HTTP requests and responses. As a result, HTTPS is far more secure than HTTP. A website that uses HTTP has http:// in its URL, while a website that uses HTTPS has https://.

47) What is postfix and exim?

Postfix is a security-oriented MTA, whereas Sendmail is standard MTA for Unix systems, and Exim is customizable and one of the most flexible mail transfer agents in terms of configuration.

48) What is postfix package?

Postfix is an open-source Mail Transport Agent ( MTA ), which supports protocols like LDAP, SMTP AUTH (SASL), and TLS. In Red Hat Enterprise Linux, the postfix package provides postfix. Run the rpm -q postfix command to see if the postfix package is installed.

49) Where are the Postfix logs?

When you run into postfix or email issues, first thing, you should check is postfix mail logs which are present in /var/log/mail. log file. It contains postfix’s general logs.

50) What is Ubuntu Postfix?

Postfix is the default Mail Transfer Agent (MTA) in Ubuntu. It attempts to be fast and secure, with flexibility in administration. It is compatible with the MTA sendmail. This section will explain installation, including how to configure SMTP for secure communications.

51) What is Postfix used for?

Postfix is a great program that routes and delivers email to accounts that are external to the system. It is currently used by approximately 33% of internet mail servers. In this article, I’ll explain how you can use Postfix to send mail using Gmail with two-factor authentication enabled.