Dovecot – A detailed explanation
By Jithin on August 22nd, 2016
Dovecot is an open source IMAP and POP3 email server for Linux/UNIX-like frameworks, created by demands for greater security. Dovecot is a fabulous decision for both little and vast establishments. It’s quick, easy to set up, requires no exceptional organization, and it utilizes almost no memory.
Dovecot can work with standard mbox, Maildir, and its own local elite dbox groups. It is completely compatible with UW IMAP and Courier IMAP servers’ execution of them, and also mail customers getting to the letter drops straightforwardly. Dovecot likewise incorporates a Mail Delivery Agent (called Local conveyance operator in Dovecot’s documentation) and a LMTP server, with discretionary Sieve sifting support. Dovecot bolsters an assortment of confirmation mappings for IMAP and POP access including CRAM-MD5 and the more secure DIGEST-MD5. With variant 2.2 some new elements have been added to Dovecot, e.g. extra IMAP order expansions, dsync has been changed or enhanced, and shared post boxes now bolster per-client flags.
By and large, a system which permits somebody to send and get email is known as a Mail User Agent or MUA. Examples of common MUAs include Mozilla Thunderbird and Microsoft Outlook Express. Whatever MUA was utilized, a message was made and sent to that client’s mail server. The mail server does not communicate with individuals specifically like the MUA does; rather, its occupation is to get email from another PC and either send it on to wherever it needs to go, or handle last conveyance of email. The “mail server” is known as a Mail Transfer Agent or MTA. The MTA then checks the message to decide the beneficiary, and inquiries the Domain Name System (DNS) servers to discover which other MTA is in charge of taking care of email for the beneficiary being referred to. It then sends the message to that MTA. Now, the message has gone from the remote client’s PC to their mail server, and has gone to the mail server which handles email for the beneficiary being referred to.
Contingent upon the system setup, it’s entirely conceivable that the message will be transferred to yet another MTA. Be that as it may, sooner or later, one MTA will assume liability for the message and get to be in charge of conveyance. As of now, the MTA will pass the message to a Mail Delivery Agent (MDA). At its center, a MDA is in charge of really putting away the message to plate. Some MDAs do different things also, for example, sifting mail or conveying to subfolders. Be that as it may, it is the MDA that stores the mail on the server.
Presently, it’s an ideal opportunity to check your mail. You start up your MUA, and it questions your mail server utilizing one of the standard protocols: IMAP or POP3. The mail server affirms your personality, then recovers the rundown of messages from the mail stockpiling territory and returns them to the MUA. Your MUA then shows those message to you, and you can now read your mail.
IMAP and POP3 are the two basic conventions utilized by MUAs to speak with mail stockpiling servers. POP3 is generally utilized by clients who do not have a fast association with the mail server. One of POP3’s fundamental standards is that MUAs downloads mail and stores it locally (on the client’s PC) and after that they erase the mail from the server. IMAP is designed for LANs and fast associations. The expectation of IMAP is to contact the server every time a given message should be perused (aside from MUA-particular reserving). Dovecot has various improvements for IMAP that make it an astoundingly decent entertainer for most IMAP situations.
Dovecot is not included with real gathering of email. That usefulness is given by a MTA such as Exim or Postfix. When email has been recieved by the MTA, then it can either be conveyed by MTA, or by another MDA. It can also be passed to the Dovecot LDA for conclusive conveyance. The decision relies on upon different variables particular to the establishment. As an IMAP and POP3 server, Dovecot gives an approach to Mail User Agents (MUAs) to get to their mail. When a client’s MUA contacts the mail server, the product which answers that solicitation is an IMAP or POP3 server. IMAP and POP3 servers take demands from MUAs and answer those solicitations by getting to email messages put away on the server and sending them out to the MUA utilizing IMAP or POP3. Dovecot is one system which can give that IMAP and POP3 server usefulness. Likewise, Dovecot gives usefulness to definite message conveyance with the Dovecot LDA (Local Delivery Agent). The LDA is in charge of putting away email messages into the message store. Nearby conveyance can be done by the MTA itself, by a different Mail Delivery Agent, or utilizing the Dovecot LDA. The decision is made by prerequisites of the specific server establishment.
Note that Dovecot is NOT in charge of accepting mail from different servers. Dovecot just handles email (a) messages leaving the neighborhood message store, going out to IMAP and POP3 customers, and (b) messages which have as of now been recieved by the MTA and are to be put away into the nearby message store. There are two essential stockpiling alternatives of mail in the *NIX world: mbox and Maildir. Mbox stores different messages – in some cases hundreds or a large number of messages – in a solitary record. Maildir stores every message a different document. Mbox and Maildir have wide backing crosswise over different email programming including MTAs and MDAs, and are both completely supported by Dovecot. Dovecot offers some mail stockpiling arrangements of its own: sdbox and mdbox.
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