There are different means of digital communication such as Voice-over-IP, mobile texts, online chat and more and all of these follow a well-defined protocol. As a matter of fact, even snail mail has proper protocols in place and the same is applicable in the case of email communications made over the internet. This protocol is referred to as hosted SMTP (Simple Message Transfer Protocol) and it enables people to send emails to their recipients directly or through specialized software referred to as SMTP servers. The process of sending and receiving emails is fairly simple at its core and it usually entails the following steps:
A message is sent by the email client to the specialized software known as the hosted SMTP server.
- The SMTP protocol is understood by the SMTP server and so it begins to authenticate the sender. The incoming message is then broken down and the domain address of the email’s recipient is sniffed out. The DNS server of the recipient’s domain is obtained and DNS entry is checked for obtaining the IP address of the recipient’s SMTP server.
- The message is then passed by the recipient’s SMTP server to its inbound counterpart, which will then unpack the message and make it available to the email client of the recipient. This counterpart can be hosted physically on the same machine as the SMTP server or can also have a different host.
- The message is held by the incoming mail server in the recipient’s inbox and the client program that’s being used by the email recipient finally pulls it out.
When it comes to outbound SMTP, it comprises of the activities that are outlined in step 2 above. The exact extent and nature may differ slightly, depending on the mail server hosting provider you use. Nonetheless, the core activities remain the same i.e. authentication of the sender, unpacking the message, checking the intended recipient’s DNS entry and then performing a ‘relay’ to the intended SMTP server if required or ensuring final delivery by sending it to the POP3/IMAP server.
Some other capabilities offered by many companies, such as DuoCircle.com, are also involved in outbound SMTP include scheduling and queuing, offering robust scalability, i.e. handling large number of emails quite frequently, dedicated IP and advanced analytics.
As far as the SMTP server is concerned, it is simply the physical component that implements the process of outbound SMTP mentioned above. It is responsible for implementing the SMTP protocol, which involved retrieving, unpackaging and then parsing messages that are sent by the email client over the wire or another SMTP server. There are also cases where the domain of the recipient is not directly connected to the SMTP server. In such situations, the message is sent to an SMTP server that’s closest to the recipient’s domain. This process is performed until the message reaches a server directly connected to the recipient’s domain, which means the email lands into the inbox of the recipient after it is relayed to another specialized software that routes the message.