Sendmail refers to the routing facility set within an internetwork email which can provide support provision for diverse transfer of mails as well as adequate delivery methods which may even include Simple Mail Transfer Protocol (SMTP) and is generally used for transporting email within the internet. It is basically the highly popular implementation method of the SMTP process with which emails can be transported through. Upon the receiving of an email, the sendmail server will then attempt to create a way out for delivering the mail to its esteemed recipient within the most immediate time frame.
In the immediate absence of such recipient, the sendmail then queues such massages only to be delivered on a later time. Generally, sendmail does not have a facility for mailbox (Lessig, 2009). This calls for other software to be used to work on the capacity of such a mailing box facility. Overview of Sendmail The underlying importance of a sendmail is to provide facilitation and support in transferring a broad category and nature of mails. It also acts as a good method for providing diverse methods of delivering mails. It is basically an internetwork email for transfer, delivery and storage of mails from one end to their recipient.
Operated from the support of various world internet servers such as Postfix, Exim and the Microsoft Exchange server, sendmail can with great flexibility help to deliver mails. It largely supports classically a wide context of email transferring protocols amongst which may include DECnet’s mail11, ESMTP, SMTP, UUCP, and others (Moody, 2001). The popularity of sendmail occurs from its basic role of facilitating transfers, delivering and queuing of mails for the retrieval by their recipients. Such development in popularity has also been from the growing demand in internet communication through emails, which can only be supported by sendmail.
How Sendmail Works (For Incoming and Outbound Mail. ) The operation and working of a sendmail usually involves an equitable balance and realization of both the incoming and the outbound mails within your mailing domain. Incoming mails Each mailing domain has it owns mailing server. All the mails that are send to such users will eventually arrive at their respective mailing servers upon which sendmail acts on them for processing before it deposits them on their respective mailboxes as provided by the operating system in use. Conceptually, a mail is not usually delivered directly to its client’s PC.
However, the user will retrieve such mails from their respective mail server with the use and help of different software which may include outlook express, Microsoft Outlook, which can adequately support with ease either IMAP or even POP mail retrieving protocols. Users who are logged into their respective mail servers will then be able to read their mails easily with the use of a general text-based client (Andress, 2003). Outbound mails The working of an outbound mail is slightly different from that of the inbound mails on the mailing server.
Workstation users using their PC are required to create a configuration of their respective email software which helps in making such mail server as been their respective mail servers for their SMTP mail server. When the outbound mail has its destination within the local perimeter, sendmail will then place such massage to their recipient’s mailbox for their retrieval with the use of the above stated methods (Lessig, 2009). However, if such an email is destined for yet another mailing domain, their will slightly be a different approach whereby sendmail will use DNS first in getting MX recording for such different domains.
From this point, the server will then try to deliver such mail to its respective mail server destination with the use of Simple Mail Transport Protocol (SMTP). Alternatives to Sendmail There are various alternatives to sendmail. These include Postfix which is a free open source mailing transfer agent and a computer program for delivering mails. Also, we have the qmail, which is generally a transfer agent for mail which however runs on Unix. Courier mail server is yet another transfer service for mails which provides IMAP and ESMTP (Andress, 2003).
EXim is also another mailing transfer agent that is done on operating systems that are Unix-like. Port Used for Sendmail The convectional port for sendmail is port 25. However, this can be configured to suit the interest of the client or organization depending of the scale of security requirements. DNS server will actually work out for this. Configuration Examples The primary port for the sendmail (port 25) can be configured to meet the security and operational demands for the user. Start by setting out the most appropriate DNS with the help on MX records in configuring the file.
With your default SMTP server, you can then edit the sendmail appropriately to suit your interest. Consequently, configuration can be done from port 25 to other user friendly ports according to the needs of the organization (Moody, 2001). Location and format of configuration files The location and configuration of sendmail files is generally done and held within the server. Files that are primary include hostnames, man pages and others. They are located and stored at the mail servers.