nixCraft » Postfix

Courier IMAP SSL Server Certificate Installtion and Configuration

Vivek Gite — Tue, 20 Jan 2009 19:38:48 +0000

The Courier mail server is a mail transfer agent (MTA) server that provides ESMTP, IMAP, POP3, webmail, and mailing list services with individual components. But, it is best known for its IMAP / IMAPs and POP3 / POP3s (secure version) server component.

Courier can provides support for both regular UNIX operating system account (stored in /etc/passwd) and virtual mail account managed by third party backends such as OpenLDAP, MySQL and so on.

In this quick tutorial, you will learn about installing Courier IMAP SSL digital certificate.

Postfix Mail Server Security Update [moderate security impact]

Vivek Gite — Mon, 18 Aug 2008 22:10:28 +0000

Postfix MTA updated to fix security vulnerabilities such as incorrectly checks the ownership of a mailbox. In some configurations, this allows for appending data to arbitrary files as root. This update has been rated as having moderate security impact.

Postfix and MS-Exchange Mail Server Affected by ORDB.org Spam Service

Vivek Gite — Thu, 27 Mar 2008 19:03:27 +0000

Since y'day I noticed one of our article related to ORDB.org spam blocker receiving lots of traffic. I received couple of calls from our clients because most emails was getting bounced via Exchange or Postfix mail server. ORDB is now configured to return each IP as spam source ORDB was a database of open relay email servers, [...]

Quick Tip: Postfix Flush the Mail Queue

Vivek Gite — Thu, 25 Oct 2007 14:09:42 +0000

Describes how to flush email queue from a shell prompt under UNIX / Linux operating system.

Postfix Illegal seek / queue file write mail server error and solution

Vivek Gite — Thu, 27 Sep 2007 17:25:30 +0000

Most mail servers are tight on resources. The Postfix system is designed to run within a finite memory budget. These limits are imposed on each and every user to avoid resource exhaustion. The idea is pretty simple, keep mail server running under conditions of stress, without making the problem worse. However some time user sends [...]

Linux Postfix SMTP (Mail Server) SSL Certificate Installations and Configuration

Vivek Gite — Thu, 12 Jul 2007 19:51:13 +0000

In this tutorial yo0u will learn about Installing SSL Certificate (Secure Server Certificate) to secure communication between Postfix SMTP server and mail client such as Outlook or Thunderbird.

Postfix mail server block Malware with blacklist

Vivek Gite — Mon, 25 Jun 2007 19:03:06 +0000

Malware is used for a harmful purpose. It can be in your software or hardware. Email and free (don't confuse with OSS) or pirated software is the most famous way to spread malware. It is inserted in a system w/o user notification. Wikipedia defines Malware as: Malware is software designed to infiltrate or damage a [...]

Postfix mail server block .bat, .exe .com .vbs mime attachments – common virus spreading files

Vivek Gite — Wed, 20 Jun 2007 19:57:44 +0000

Postfix provides Mime header check for all incoming messages. You can put restrictions on .exe / .bat / .vbs files and block all attachments. mime_header_checks directive allows you to define file, you will place a restriction for any file extensions that you do not want to have passing through your mail sever system. On most mail server [...]

How to setup Linux antivirus and antispam mail server

Vivek Gite — Wed, 07 Feb 2007 15:00:28 +0000

Librenix has a posted small and sweet article that explains basic steps to configure and install a mail server with antivirus / antispam in minutes. From the article: This article illustrates a situation where you need to set up your own mail server (be it your home mail server, or a small office one). It actually shows [...]

Postfix configure anti spam with blacklist

Vivek Gite — Tue, 09 Jan 2007 12:23:51 +0000

Postfix is free and powerful MTA. You can easily configure Postfix to block spam. You need to add following directives to /etc/postfix/main.cf file: => disable_vrfy_command = yes : Disable the SMTP VRFY command. This stops some techniques used to harvest email addresses. => smtpd_delay_reject = yes : It allows Postfix to log recipient address information when rejecting a [...]

Postfix masquerading or changing outgoing SMTP email or mail address

Vivek Gite — Thu, 28 Dec 2006 10:35:04 +0000

Address rewriting allows changing outgoing email ID or domain name itself. This is good for hiding internal user names. For example: SMTP user: tom-01 EMAIL ID: tom@domain.com Server name: server01.hosting.com However when tom-01 send an email from shell prompt or using php it looks like it was send from tom-01@server01.hosting.com In some cases internal hosts have no valid Internet [...]

ORDB.org RBL Anti Spam service going offline

Vivek Gite — Mon, 18 Dec 2006 18:22:26 +0000

Email filtering is an essential task. There are many methods like: => Bayesian spam filtering => SpamAssassin/DSPAM programs => Check open relay using RBL etc Now ORDB.org is shutting down its operation. ORDB is quite effective and I use this list against all of email servers. Spammers still use 3rd party servers and desktop computers so that they [...]

PHP Send Email Using Authenticated SMTP Mail Server In Real Time

Vivek Gite — Thu, 30 Nov 2006 19:56:23 +0000

PHP has mail() function to send an email to users. However this mail() will not work: => If sendmail (or compatible binary) is not installed => If Apache Web server / Lighttpd running in chrooted jail => And your smtp server needs an authentication before sending an email => Or you just need to send email using PHP PEAR In [...]

Monitor and restart Apache or lighttpd webserver when daemon is killed

Vivek Gite — Tue, 21 Nov 2006 11:26:39 +0000

When you cannot monitor your server for service availability, it is better to take help of automated monitor and restart utility. Last 4 days I was away from my server as I was enjoying my vacation. During this time due to load my lighttpd webserver died but it was restarted automatically within 2 minutes. I had utility configured for monitoring services on a Linux system called monit. It offers all features you ever needed for system monitoring and perform error recovery for UNIX like system.

Setup sendmail php mail() support for chrooted Lighttpd or Apache web server

Vivek Gite — Wed, 08 Nov 2006 05:04:57 +0000

Once chroot() call is applied to chrooted lighttpd or apache web server, you lost the connection with real /usr/sbin/sendmail program. The php mail() function allows you to send mail. For the Mail functions to be available, PHP must have access to the sendmail binary on your system during compile time. If you use another mail [...]

Postfix mail server limit the mailbox size

LinuxTitli — Sat, 28 Oct 2006 23:26:36 +0000

So how do you limit the mailbox size for users configured with the Postfix mail server? It is good choice to avoid problem (disk DoS) by limiting mailbox size. This will avoid the user or hacker to eat up all hard disk space. Display the default mailbox size limit Type the following command: # postconf mailbox_size_limit Output: mailbox_size_limit = 51200000 51200000 bytes [...]

Test mail server for an open relay

Vivek Gite — Fri, 27 Oct 2006 13:23:50 +0000

I don't want let spammers take control of my mail server, I have configured my mail server but I am not sure how do I test my mail server for open relay? But what is an open mail realy? An open mail relay occurs when a mail server processes a mail message where neither the sender [...]

How to redirect one users mail to another user with postfix

Vivek Gite — Tue, 26 Sep 2006 18:39:38 +0000

Postfix is an open source mail transfer agent (MTA), for the routing and delivery of email. It provides a method of redirect mail to another user for both local and remote users. You need to configure /etc/postfix/aliases (or use /etc/aliases) file. The aliases file (read as table) provides a system-wide mechanism to redirect [...]

Force sendmail to deliver a message in sendmail’s mail queue

nixcraft — Mon, 03 Apr 2006 00:26:00 +0000

Sendmail is age-old mail transfer agent (MTA). We still use sendmail on Solaris boxes and all other web hosting (www) server to route mails via our master MTA. Task: Linux/UNIX deliver old email The command sendmail -q forces the mail queue to be sent. Use the command mailq to find out what's in the queue: # sendmail -q # [...]