Simple Mail Transfer Protocol (SMTP) Interview Questions & Answers

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Simple Mail Transfer Protocol (SMTP) Interview Questions & Answers

Experienced in Simple Mail Transfer Protocol (SMTP)? Simple Mail Transfer Protocol (SMTP) is very known to everyone in IT industry. It is the standard for sending mail electronically. Firstly the mail is sent to the SMTP server by a TCP connection. SMTP server is always listening to the port. Even though many other jobs are present, Simple Mail Transfer Protocol (SMTP) job is unique. Good hands on knowledge on these concepts will put you ahead in interview. Every where we can find job opportunities for this position. Wisdomjobs has interview questions which are exclusively designed for employees to assist them in clearing interviews. Simple Mail Transfer Protocol (SMTP) interview questions and answers are useful for employees who are good at SMTP technology.

Simple Mail Transfer Protocol (SMTP) Interview Questions

Simple Mail Transfer Protocol (SMTP) Interview Questions
    1. Question 1. What Is Smtp?

      Answer :

      Logging into your email account to retrieve email seems fairly simple. However, there is technology working behind the scenes, such as simple mail transfer protocol (SMTP) and internet networks to ensure you can send and receive email. Think about SMTP as a mail carrier, sorting and delivering messages to mail servers. These messages are then delivered directly to your email inbox.

    2. Question 2. Explain How Smtp Evolved?

      Answer :

      Electronic messaging was created decades before the internet revolution. In the 1960s people were exploring how to communicate using mainframe computers. The U.S. Government was the first to create a server to transmit email. In the 1970s, the mailbox protocol was developed, which was an early version of SMTP. The modern version of this technology was developed in 1982.

    3. Question 3. Explain How Does Smtp Work?

      Answer :

      SMPT is responsible for transmitting email across Internet networks (IPs). This technology is used specifically for sending outgoing email. Clients typically use applications such as Internet Message Access Protocol (IMAP) or Post Office Protocol (POP) to access to their email box. For example, if you send an email it goes to a mail server using SMTP. The mail client will then deliver it to the user's mailbox.

    4. Question 4. Explain The Smtp Basic Functions?

      Answer :

      SMTP is responsible for a little more then just deliver messages to servers. It performs several functions that streamlines the delivery process.

      • It evaluates the configuration and grants permission to the computer who is trying to send a message.
      • It can also track if the message was sent successfully. If it isn't, an error message is sent to the sender.
      • Extended SMTP is a little more advanced then older versions. It helps cut back on email spam.

    5. Question 5. Explain Resolved Limiting Factors Of Smtp?

      Answer :

      Previous versions of this technology had limiting figures, such as the location of the client within the network. SMTP allows clients to submit emails quickly regardless of the recipients location. Thats because current SMTP technology uses a clients authentication (which are their accreditations) instead of the license IP address to send email.

    6. Question 6. What Do You Know About Other Protocols?

      Answer :

      In order for computers to communicate with one another, standard methods of information transfer and processing have been devised. These are referred to as "protocols" and some of the more common ones such as TCP, IP, UDP, POP, SMTP, HTTP, and FTP

    7. Question 7. What Is Istp Protocol?

      Answer :

      The InterStream Transit Protocol (ISTP) is a secure protocol that allows Internet Service Providers (ISPs) to offer high bandwidth multimedia services over their networks. The ISTP application is installed as a new protocol handler into browsers. It includes components which enable Internet Service Providers to obtain incremental revenue from subscribers, advertisers, other ISPs, and streaming video providers in exchange for using premium bandwidth services on their networks.

    8. Question 8. Are Email Addresses Case Sensitive?

      Answer :

      Yes, In email address before the @, are case senstive. So email address is case-sensitive.

    9. Question 9. What Is The Meaning Of Return-path, Reply-to And From?

      Answer :

      From: <fromemail example.com="">
      To: <you example.com="">
      Reply-To: <replyto example.com="">
      </replyto></you></fromemail>

      • Return-path: If email is failed to deliver OR bounced, then email will return to return-path.
      • Reply-to: If someone reply on email, then email will be goes to reply-to.
      • From: It denote from where which email-address came.

    10. Question 10. What Is The Difference Between Ports 465 And 587?

      Answer :

      Both are protocol.

      465 is for SMTPS protocol, In this SSL encryption is started automatically before any SMTP level communication.

      587 is for MSA protocol. SSL encryption may be started by STARTTLS command at SMTP level(if server supports). In this ISP does not filter server's EHLO reply.It helps to stop outgoing spam email. 

    11. Question 11. How To Check If An Email Address Exists Without Sending An Email?

      Answer :

      You can to execute below command.

      RCPT TO: useremail@domain.com

      This identifies the recipient of the email message. This command can be repeated multiple times for a given message in order to deliver a single message to multiple recipients.

    12. Question 12. What Are Test Email Recipients? Or Which Email Address I Can Use For Sending Test Email?

      Answer :

      Following are testing email address

      t11111@no-spam.ws
      t11112@no-spam.ws
      t11113@no-spam.ws
      t11114@no-spam.ws
      t11115@no-spam.ws

    13. Question 13. How To Check If Smtp Is Working From Commandline?

      Answer :

      telnet {smtp_domain_name} {smtp_port}

    14. Question 14. What Is The Extension Model Of Smtp?

      Answer :

      In an effort that started in 1990, approximately a decade after RFC  821 was completed, the protocol was modified with a "service extensions" model that permits the client and server to agree to utilize shared functionality beyond the original SMTP requirements.

      The SMTP extension mechanism defines a means whereby an extended SMTP client and server may recognize each other, and the server can inform the client as to the service extensions that it supports.

      The extension framework consists of:

      • The SMTP command EHLO, superseding the earlier HELO,
      • a registry of SMTP service extensions,
      • additional parameters to the SMTP MAIL and RCPT commands, and
      • optional replacements for commands defined in this protocol, such as for DATA in non-ASCII transmissions.

    15. Question 15. What Is Definition And Registration Of Extensions?

      Answer :

      The IANA maintains a registry of SMTP service extensions. A corresponding EHLO keyword value is associated with each extension.

      Each service extension registered with the IANA must be defined in a formal standards-track or IESG-approved experimental protocol document. The definition must include:

      • the textual name of the SMTP service extension;
      • the EHLO keyword value associated with the extension;
      • the syntax and possible values of parameters associated with the EHLO keyword value;
      • any additional SMTP verbs associated with the extension (additional verbs will usually be, but are not required to be, the same as the EHLO keyword value);
      • any new parameters the extension associates with the MAIL or RCPT verbs;
      • a description of how support for the extension affects the behavior of a server and client SMTP; and,
      • the increment by which the extension is increasing the maximum length of the commands MAIL and/or RCPT, over that specified in this standard.

      In addition, any EHLO keyword value starting with an upper or lower case "X" refers to a local SMTP service extension used exclusively through bilateral agreement.  Keywords beginning with "X" MUST NOT be used in a registered service extension. Conversely, keyword values presented in the EHLO response that do not begin with "X" MUST correspond to a standard, standards-track, or IESG-approved experimental SMTP service extension registered with IANA. A conforming server MUST NOT offer non-"X"-prefixed keyword values that are not described in a registered extension.

      Additional verbs and parameter names are bound by the same rules as EHLO keywords; specifically, verbs beginning with "X" are local extensions that may not be registered or standardized.  Conversely, verbs not beginning with "X" must always be registered.

    16. Question 16. What Are Mail Objects?

      Answer :

      SMTP transports a mail object.  A mail object contains an envelope and content.

      The SMTP envelope is sent as a series of SMTP protocol units.  It consists of an originator address (to which error reports should be directed); one or more recipient addresses; and optional protocol extension material.  Historically, variations on the recipient address specification command (RCPT TO) could be used to specify alternate delivery modes, such as immediate display; those variations have now been deprecated.

      The SMTP content is sent in the SMTP DATA protocol unit and has two parts: the headers and the body. If the content conforms to other contemporary standards, the headers form a collection of field/value pairs structured as in the message format specification ; the body, if structured, is defined according to MIME.  The content

      is textual in nature, expressed using the US-ASCII repertoire.

      Although SMTP extensions (such as "8BITMIME") may relax this restriction for the content body, the content headers are always encoded using the US-ASCII repertoire.  A MIME extension defines an algorithm for representing header values outside the US-ASCII repertoire, while still encoding them using the US-ASCII repertoire.

    17. Question 17. What Are Senders And Receivers?

      Answer :

      In RFC 821, the two hosts participating in an SMTP transaction were described as the "SMTP-sender" and "SMTP-receiver".  This document has been changed to reflect current industry terminology and hence refers to them as the "SMTP client" (or sometimes just "the client") and "SMTP server" (or just "the server"), respectively.  Since a given host may act both as server and client in a relay situation, "receiver" and "sender" terminology is still used where needed for clarity.

    18. Question 18. What Are Mail Agents And Message Stores?

      Answer :

      Additional mail system terminology became common after RFC 821 was published and, where convenient, is used in this specification. In particular, SMTP servers and clients provide a mail transport service and therefore act as "Mail Transfer Agents" (MTAs). "Mail User Agents" (MUAs or UAs) are normally thought of as the sources and targets of mail. At the source, an MUA might collect mail to be transmitted from a user and hand it off to an MTA; the final ("delivery") MTA would be thought of as handing the mail off to an MUA (or at least transferring responsibility to it, e.g., by depositing the message in a "message store").  

      However, while these terms are used with at least the appearance of great precision in other environments, the implied boundaries between MUAs and MTAs often do not accurately match common, and conforming, practices with Internet mail. Hence, the reader should be cautious about inferring the strong relationships and responsibilities that might be implied if these terms were used elsewhere.

    19. Question 19. What Is Host?

      Answer :

      For the purposes of this specification, a host is a computer system attached to the Internet (or, in some cases, to a private TCP/IP network) and supporting the SMTP protocol. Hosts are known by names (see "domain"); identifying them by numerical address is discouraged.

    20. Question 20. What Is Domain?

      Answer :

      A domain (or domain name) consists of one or more dot-separated components. These components ("labels" in DNS terminology ) are restricted for SMTP purposes to consist of a sequence of letters, digits, and hyphens drawn from the ASCII character set.  Domain names are used as names of hosts and of other entities in the domain name hierarchy. For example, a domain may refer to an alias (label of a CNAME RR) or the label of Mail eXchanger records to be used to deliver mail instead of representing a host name.

      The domain name, as described in this document and in, is the entire, fully-qualified name (often referred to as an "FQDN"). A domain name that is not in FQDN form is no more than a local alias.

      Local aliases MUST NOT appear in any SMTP transaction.

    21. Question 21. What Are Buffer And State Table?

      Answer :

      SMTP sessions are stateful, with both parties carefully maintaining a common view of the current state.  In this document we model this state by a virtual "buffer" and a "state table" on the server which may be used by the client to, for example, "clear the buffer" or "reset the state table," causing the information in the buffer to be discarded and the state to be returned to some previous state.

    22. Question 22. What Is Lines?

      Answer :

      SMTP commands and, unless altered by a service extension, message data, are transmitted in "lines". Lines consist of zero or more data characters terminated by the sequence ASCII character "CR" (hex value 0D) followed immediately by ASCII character "LF" (hex value 0A).

      This termination sequence is denoted as in this document.

      Conforming implementations MUST NOT recognize or generate any other character or character sequence as a line terminator.  Limits MAY be imposed on line lengths by servers.

      In addition, the appearance of "bare" "CR" or "LF" characters in text (i.e., either without the other) has a long history of causing problems in mail implementations and applications that use the mail system as a tool. SMTP client implementations MUST NOT transmit these characters except when they are intended as line terminators and then MUST, as indicated above, transmit them only as a  sequence.

    23. Question 23. What Are Originator, Delivery, Relay, And Gateway Systems?

      Answer :

      This specification makes a distinction among four types of SMTP systems, based on the role those systems play in transmitting electronic mail.  An "originating" system (sometimes called an SMTP originator) introduces mail into the Internet or, more generally, into a transport service environment. A "delivery" SMTP system is one that receives mail from a transport service environment and passes it to a mail user agent or deposits it in a message store which a mail user agent is expected to subsequently access.  A "relay" SMTP system (usually referred to just as a "relay") receives mail from an SMTP client and transmits it, without modification to the message data other than adding trace information, to another SMTP server for further relaying or for delivery.

      A "gateway" SMTP system (usually referred to just as a "gateway") receives mail from a client system in one transport environment and transmits it to a server system in another transport environment.

      Differences in protocols or message semantics between the transport environments on either side of a gateway may require that the gateway system perform transformations to the message that are not permitted to SMTP relay systems.  For the purposes of this specification, firewalls that rewrite addresses should be considered as gateways, even if SMTP is used on both sides of them.

    24. Question 24. What Are Message Content And Mail Data?

      Answer :

      The terms "message content" and "mail data" are used interchangeably in this document to describe the material transmitted after the DATA command is accepted and before the end of data indication is  transmitted. Message content includes message headers and the possibly-structured message body. The MIME specification provides the standard mechanisms for structured message bodies.

    25. Question 25. What Is Mailbox And Address?

      Answer :

      As used in this specification, an "address" is a character string that identifies a user to whom mail will be sent or a location into which mail will be deposited.  The term "mailbox" refers to that depository. The two terms are typically used interchangeably unless the distinction between the location in which mail is placed (the mailbox) and a reference to it (the address) is important. An address normally consists of user and domain specifications.  The standard mailbox naming convention is defined to be "local- part@domain": contemporary usage permits a much broader set of applications than simple "user names".  Consequently, and due to a long history of problems when intermediate hosts have attempted to optimize transport by modifying them, the local-part MUST be interpreted and assigned semantics only by the host specified in the domain part of the address.

    26. Question 26. What Is Reply?

      Answer :

      An SMTP reply is an acknowledgment (positive or negative) sent from receiver to sender via the transmission channel in response to a command.  The general form of a reply is a numeric completion code (indicating failure or success) usually followed by a text string.

      The codes are for use by programs and the text is usually intended for human users. Recent work has specified further structuring  of the reply strings, including the use of supplemental and more specific completion codes.

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