The MTA can use its own user list, system list, LDAP or AD user lists for authorization. However, it is quite possible for an MTA to receive mail from trusted users, for example, from the company's local network, without authorization. anyone can use our server to send mail, and spammers will be delighted! Currently, open relays occur mainly due to server configuration errors. After authorizing the user, the MTA accepts the message and tries to deliver it further.Īctually, authorization is not a mandatory procedure for the MTA, but without authorization, we will get an open relay, i.e. The mail client connects to the MTA using the SMTP protocol and first communicates its credentials. For Ivanov, the process of sending mail consists of creating a message and pressing the "Send" button in the mail client. In our example, the user Ivanov, located in the domain ( ), writes a letter to Kozlov in the domain ( ). Let's see what happens when sending mail. Also MDA, its failure does not lead to the inoperability of the mail server, only the receipt of mail by the mail client becomes unavailable, at the same time it can be easily accessed in other ways, for example, through the web interface. If the postman is sick, then this will not affect the work of the post office, you just will not receive letters at home. To draw an analogy, you can imagine the MTA as a post office that receives and sends mail, and the MDA with the postman who brings the incoming correspondence to your home. MDA can work using the POP3 or IMAP protocols, in some cases, to "communicate" the mail client and the delivery agent, their own protocols with extended functionality, such as MAPI (Exchange Server), can be used.Ĭontrary to popular misconception, MDA has nothing to do with the mail transfer process. Here comes the stage MDA ( Mail Delivery Agent- mail delivery agent), its task, at the request of the mail client, is to transfer mail to it from the mailbox on the server. However, progress does not stand still, MTA, receiving a letter, places it in the user's mailbox on the server to which the latter must access, preferably in the most simple and understandable way.
Once upon a time, this was exactly the case, and in order to access your mailbox, you needed to have certain technical knowledge.
MTA works on the SMTP protocol, and one of them, in principle, is already enough to create an e-mail system. Very often (in Linux/UNIX) the MTA is also referred to as a mail server. The most important part of the mail server is MTA ( Mail Transfer Agent- mail forwarding agent) whose tasks include receiving and transmitting mail. Let's take a look at the structure of the mail server and what happens when a user tries to send mail.
Serialmailer could not connect to smtp server software#
Unlike Windows, where the mail server is a complete software solution and the developers have already taken care of internal interaction, in Linux, the mail server components are separate programs and you need to configure their interaction yourself. This is especially important for administering servers on the Linux platform. However, there is a whole mechanism hidden inside, understanding the operation of which is key to successfully setting up and maintaining an e-mail system. All interaction with such a server consists in addressing the mail client to certain ports, or even through the web interface. In our opinion, for the sake of administering one or two entry-level mail servers, it is not at all necessary to become a specialist in the field of e-mail.įor most users and novice administrators, the mail server is a kind of "black box", which, having received a letter, delivers it to the addressee by "unknown" ways and vice versa. This material contains quite a lot of simplifications and generalizations in order to give system administrators the necessary minimum knowledge.
In this article, we will consider the structure and principle of operation of mail servers, without understanding which, setting up an email system is quite capable of turning into shamanic dances with a tambourine. This is not surprising, a mail server has a much more complex structure than a file server, router or terminal server. Many system administrators experience certain difficulties when working with e-mail systems.
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