Mailservers Interview Questions and Answers

[Nimy]

1. 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.
2. What is postfix and which default port is used by postfix ?
Postfix is a open source MTA (Mail Transfer agent) which is used to route & deliver emails. It is the alternate of widely used Sendmail MTA. Default port for postfix is 25.
3. What is the role of MUA ?
MUA stands for Mail User Agent. MUA helps to read messages from the disk and display them for the user with access to the mailbox file, directly or through a network file system. This is generally a console or webmail application running on the server.
4. On which ports sendmail and senmail with SSL works ?
By default, Sendmail uses TCP and UDP port 25 for non-encrypted transfers. If the
Sendmail server is configured to use SSL for encrypting sent and received emails, it uses
port 465.
5. What are the configuration files of postfix server ?
There are two main configuration files for postfix :
• /etc/postfix/main.cf : This file holds global configuration options. They will be applied to all instances of a daemon, unless they are overridden in master.cf
• /etc/postfix/master.cf : This file defines runtime environment for daemons attached to services. Runtime behavior defined in main.cf may be overridden by setting service specific options.
6. What is Clamav-Milter ?
It is a tool to integrate sendmail and clamAV antivirus.
7. What is LMTP ?
The Local Mail Transport Protocol (LMTP) is a different mail transport protocol described in RFC 2033. It utilizes a set protocol similar to SMTP for delivering messages to the local host. Postfix can be configured to deliver messages to local users using LMTP if desired.
8. What is MTA and what is it’s role in mailing system ?
MTA Stands for Mail Transfer Agent. MTA receives and delivers email. It also determines message routing and possible address rewriting. Locally delivered messages are handed off to an MDA for final delivery. Examples are Qmail, Postfix, Sendmail etc…
9. What is MDA ?
MDA stands for Mail Delivery Agent. It is a program that handles final delivery of messages for a system's local recipients. MDAs can often filter or categorize messages upon delivery. An MDA might also determine that a message must be forwarded to another email address. Example is Procmail.
10. What is the use of postmaster account in Mailserver ?
An email administrator is commonly referred to as a postmaster. An individual with postmaster responsibilities makes sure that the mail system is working correctly, makes configuration changes, and adds/removes email accounts, among other things.
11. 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.
12. What is relay host in postfix ?
Relay host is the smtp address , if mentioned in postfix config file , then all the incoming mails be relayed through smtp server.
13. 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.
14. What is the importance of SPF records in mail servers ?
SPF (Sender Policy Framework) is a system which helps domain owners to 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.

[orarry]

What is LDAP?
Why LDAP is called light weight?
What is "LDIF"?
Which is the main configuration file for LDAP server?
What is the relationship between LDAP and JNDI?
What is SLDAP?
What is HDB?
Explain modulepath directive?
Explain moduleload directive?
How will you verify LDAP configuration file?

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