電子郵件提交代理人
出自KMU Wiki
郵件提交代理人或生活津貼 ，是一種計算機程序或者軟件代理接收電子郵件從一個郵件用戶代理 （ MUA ）和合作與郵件傳輸代理 （ MTA ）為交付的郵件。
許多多邊貿易協議作為生活津貼，以及，但也有一些程序是專為衛生和社會保障部沒有充分的MTA功能。 Historically in Internet mail , both MTA (acceptance of locally-destined mail from other domains) and MSA (acceptance of submitted mail from local users) functions were both performed by MTAs using the same protocol ( SMTP ).歷史上在網際網路郵件 ，雙方的MTA （接受當地注定郵件從其他域）和MSA （接受提交的郵件從本地用戶）的職能，均執行多邊貿易協議使用相同的協議（ SMTP ） 。
Separation of the MTA and MSA function produces several benefits:分離的MTA和MSA功能產生幾個好處：
One benefit is that an MSA, since it is interacting directly with the author's MUA, can correct minor errors in a message's format (such as a missing Date , Message-ID , To fields, or an address with a missing domain name) and/or immediately report an error to the author so that it can be corrected before it is sent to any of the recipients.好處之一是，一生活津貼，因為它是互動，直接與作者的mua ，可以糾正小錯誤 ，在一個信息的格式（如一名失踪的日期 ， 郵件ID ，領域，或地址與一名失踪的網域名稱）和/或立即報告錯誤給作者，以便它能夠得到糾正之前，這是發送到任何收件人。 An MTA accepting a message from another site cannot reliably make those kinds of corrections, and any error reports generated by such an MTA will reach the author (if at all) only after he has already sent the message. MTA的接受訊息，從另一個網站不能可靠地使這些種的更正，以及任何的錯誤報告所產生的這樣一個MTA將達到作者（如果在所有） ，只有後，他已經發出的信息。
Another benefit is that separating the MTA and MSA functions makes it easier for an MTA to deny relaying , that is to refuse any mail that is not addressed to a recipient at a domain that is served locally.另一個好處是，分離和MSA的MTA的功能，使更容易的MTA 拒絕轉播 ，那就是拒絕任何郵件，這不是給收件人在一個域是服務當地。 By contrast, an MSA must generally accept mail for any recipient on the Internet, though it only accepts such mail from authors who are authorized to use that MSA and who have established their identity to the MSA via authentication.相比之下，生活津貼，必須普遍接受郵件的收件人的任何互聯網上，雖然只接受這樣的郵件從作者是誰授權使用特派任務生活津貼和誰建立了自己的身份，向海事局通過驗證。 In times when both mail submission and acceptance of incoming mail were usually accomplished using the same protocol and the same server, the ability to send mail to arbitrary destinations without authentication allowed spammers to use MTAs as a means of distributing spam (since a single message transaction can request that an MTA relay a message to a large number of recipients), and also made it more difficult to trace a message to its origin.在的時候都電子郵件提交和接受傳入郵件，通常是完成了使用相同的協議和在同一台服務器上，有能力將郵件發送給任意目的地未經驗證，讓垃圾郵件發送者使用的多邊貿易協議作為一種手段，分發垃圾郵件 （因為一個單一的信息交易可以要求MTA的繼電器訊息給了大量的受助人） ，也發了言，它更難以追查一個信息，其原產地。
Yet another benefit is that MSAs and MTAs can have different policies for filtering of spam .然而，另一個好處是，衛生和社會保障部和多邊貿易協議可以有不同的政策，為過濾垃圾郵件 。 Most MSAs require authentication in the form of a username and password provided by the author.最衛生和社會保障部要求身份驗證，在形式的用戶名和密碼所提供的作者。 Any messages received by such an MSA are therefore traceable to an author who has a direct relationship with the MSA, and who can be held accountable for his actions.任何郵件收到這樣的生活津貼，因此可追溯至1作者誰有著直接的關係，與生活津貼，以及誰可以追究他的行動。 This allows the MSA to have either no spam filtering, or more permissive spam filtering than an MTA that exists for the purpose of accepting incoming email from other domains.這使得管理參議署有或者沒有的垃圾郵件過濾，或更寬容的垃圾郵件過濾比MTA的存在為目的，接受傳入的電子郵件從其他領域。 It is difficult to establish trust in mail sent between arbitrary domains, because there is generally no direct relationship between those domains via which trust, or even identity, can be established.這是很難建立信任，在寄出的郵件之間的任意域，是因為有一般沒有直接的關係，這些領域通過，其中信託，或什至身份，得以確立。 In the absence of such trust, an MTA must generally rely on heuristics and third-party reputation services to distinguish spam from legitimate traffic, and both of these mechanisms have a history of being error-prone.在沒有這種信任，一個普遍的MTA必須依賴於啟發式和第三黨的聲譽，服務，以區分垃圾郵件來自合法的交通，雙方在這些機制有一個歷史上被容易出錯。 The separation of MSA and MTA therefore avoids the use of unreliable spam recognition mechanisms during mail submission, and increases the probability for legitimate mail to be delivered successfully.分離的生活津貼和MTA因此，避免使用不可靠的垃圾郵件的識別機制，在郵件提交的意見書，並增加了概率為合法郵件被成功傳遞。
Implementation 實施
Many internet service providers and enterprise or institution networks restrict the ability to connect to remote MTAs on port 25 (the usual SMTP port).許多互聯網服務提供商和企業或機構網絡限制的能力，連接到遠程多邊貿易協議端口25 （通常SMTP端口） 。 Availability of a Mail Submission Agent on port 587 enables nomadic users to continue to send mail via their preferred submission servers even from within others' networks.提供郵件提交劑對端口587 ，使游牧用戶繼續發送郵件，通過他們的首選提交服務器，甚至從別人的網絡。 Using a specific submission server is a requirement when sender policies are enforced.使用特定的意見書服務器是一個要求時， 發件人的政策得到執行。
Most of the benefits mentioned above may also apply to authenticated MTA, that is port 25 after the user logs in. In fact, the relevant server software is often the same for both services.大部分的利益，上述可能也適用於驗證的MTA ，這是港口25後，用戶登錄英寸事實上，有關服務器軟件，往往是都一樣的服務。 However, the very fact that the service can be made available on a different port can be considered a further benefit, as it allows to circumvent restrictions on port 25.不過，很事實，即服務可提供對不同的連接埠可以考慮的另一個好處，因為它允許以規避限制，端口25 。
