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Mail Transfer Agent: MTA is an email gateway. i.e. Cisco Email Security Appliance (ESA)
DNS MX record: An MX record, or mail exchanger record, is a record that specifies the mail server (MTA) responsible for receiving email for its domain. MX records can prioritize servers when multiple mail servers exist in the domain.
DNS A record: Used to locate the IP address of the MTA specified by the MX record.
Groupware server: A server that accepts, forwards, delivers, and stores messages on behalf of users who only need to connect to the email infrastructure. It also manages collaborative schedules, maintains calendars, and performs other related services to members interacting within a group.
SMTP client: initiate the connection request to an SMTP server.
SMTP server: Will receive the connection request from the SMTP client.Â
Mail user agent: The MUA is a software client application like Outlook, groupware
Post Office Protocol: The POP is an application-layer protocol used by the MUA to retrieve email from a mail server. Listens on TCP port 110. POP3* When the messages are downloaded, they are deleted from the email server.
Internet Message Access Protocol: The IMAP is also an application-layer protocol that is used by the MUA to retrieve email from a mail server. An IMAP server typically listens on TCP port 143. Virtually all modern email clients (mail user agent) support IMAP. IMAP allows you to access your email wherever you are, from any device. IMAP and the POP3 are the two most prevalent standard protocols for email retrieval.
Messaging Application Programming Interface: The MAPI is also an application-layer protocol that is used by the MUA to retrieve email from a mail server and is primarily associated with Microsoft Exchange and Microsoft Outlook. It performs the services similar to IMAP but also provides other groupware functions that are associated with Outlook and Exchange
The following are examples of DNS resource record types:
A record: Used to map host names to the IPv4 address of the host. In an A record, multiple IP addresses can correspond to a single hostname. There can also be multiple host names each of which maps to the same IP address. There must be a valid A record in the DNS for the host.domain.name in order for a command, such as telnet host.domain.name, to work.
AAAA record: AAAA is used to map hostnames to the IPv6 address of the host.
MX record: MX maps a domain name to a list of mail servers for that domain.
PTR record: A PTR points to a canonical name. The most common use is for implementing reverse DNS lookups, mapping an IP address to the hostname.
NS record: An NS record identifies the DNS servers that are responsible (authoritative) for a zone.
CNAME record: A CNAME record is used to specify that a domain name is an alias for another domain name, which is the "canonical" domain name.
TXT record: A TXT record is used to associate any arbitrary text with a hostname. This record type is only used in specific cases such as Domain Keys Identified Mail, used as a method to detect email spoofing.
SOA record: Each zone contains an SOA record. The SOA record identifies the name server that is the best source of information for the data within the zone. The SOA record also contains various other parameters that define the behavior of the DNS server.
A record: Using the nslookup utility, it shows that the dmz.secure-x.public host that is resolved to the IP address of 192.0.2.50 from the 209.165.200.233 DNS server, and the 209.165.200.233 DNS server is not the authoritative DNS server for the secure-x.public domain.