MTA（Mail Transfer Agent ）：邮件传送代理，由「邮件服务器」扮演 MTA 角色，负责完成 MUA (邮件使用代理，即 Outlook Express 等邮件收发软件)传送信件的请求，将邮件从一个 MTA ( 您的邮件服务器 )传到另一个 MTA（对方的邮件服务器）。因此，简单地说，MTA 错误讯息代码，即是由邮局( 邮件服务器 )来函告知您寄信不成功与退信原因。
MTA 错误代码的表现方式如 550 5.1.1 ，由两大部份组成：「SMTP 代码」与「DSN 代码」所组成。以 550 5.1.1 为例，550 为 SMTP 代码， 5.1.1为 DSN 代码。SMTP 代码固定为三位数字， DSN 代码固定为由小数点隔开的三个数字。
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#用于限定系统所接受的最大的单封邮件长度。限制postfix队列文件的大小。缺省值为#10240000 bytes。
message_size_limit = 1572864000
#限制信头长度。缺省值为102400bytes
#header_size_limit =
#这是用于设定当SMTP连接来时，要显示的版本资讯
smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU)
# biff是一个能在收到新邮件时，发出通知给本地用户的小程序。如果你的用户不会登录邮#件系统，建议你关掉biff通知，因为这有助于提升邮件系统得效率。
biff = no 继续阅读 »
postfix有四种不同的邮件队列，并且由队列管理进程统一进行管理：
1． maildrop：本地邮件放置在maildrop中，同时也被拷贝到incoming中。
2． incoming：放置正在到达或队列管理进程尚未发现的邮件。
3． active：放置队列管理进程已经打开了并正准备投递的邮件，该队列有长度的限制。
postfix提供了一组命令行工具来检查、控制、管理队列里的邮件，其中以postsuper和postqucuc这两个工具最为重要。你可以对队列中的邮件进行下列操作：显示邮件列表,删除邮件,重新排队,保留邮件,显示邮件内容,清空邮件 继续阅读 »
In this guide you will learn how to tweak the default Falko mail guide for Postfix (+Auth SMTP + Quota), setup to better combat SPAM and allow a little bit of backward compatibilty of the older Qmail systems.
So lets get started…
The HowtoForge guide is great for everything however if you have a very busy mail server running Spam Assasin on 1000s of message per minute is a CPU killer. The best answer is to stop the mail before it hits Spam Assasin with a range of RBL (Realtime Blacklists) and RHBL (Same but different), Greylistings and Helo Checks. 继续阅读 »
If you get hit by a spam attack that floods your server with hundreds/thousands of emails from the same sender email address or to the same recipient email address, you can clean your mail queue from these emails with one single command before the mail flood takes your server to its knees.
You can check your current mail queue like this:
Since Postfix version 2.3, Postfix supports custom bounce messages. This guide shows how to configure custom Postfix bounce messages.
I do not issue any guarantee that this will work for you!
1 Postfix Version
First you should find out about your Postfix version to make sure it supports custom bounce messages:
If you are administrating a mail server and use blacklists to block spam (like in this article: How To Block Spam Before It Enters The Server (Postfix)), you probably know this problem: from time to time your customers complain that they cannot receive emails from certain freemailers. Most often this happens because a freemailer was abused to send out spam and therefore got blacklisted. This short guide shows how you can whitelist such a mail server in Postfix to make your customers happy again.
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