Postfix

Postfix 2.9 Upgrade
To help reduce the load on my Postfix mail servers, I rely on Postscreen (which is built in to Postfix) to help weed out bot spam and misconfigured mailers. And to reduce the load on Postscreen, one of my tricks is to whitelist the outbound IP addresses of a couple of […]

Postscreen Whitelisting of SMTP Outbound IP Addresses from Large Webmail ...

This entry was posted in Linux Technology and tagged CIDR Gmail Hotmail Microsoft Outlook Outlook.com Postfix Postscreen white list whitelist Yahoo on by (updated 3175 days ago)
Postfix 2.9 Upgrade 5
I run a number of “real” Postfix servers that live “away from home,” in a cozy server cabinet at our colo facility, but I also like to keep a Postfix server handy in the basement, running on an ancient (but rock solid) Dell PowerEdge 2450 running CentOS 5. I don’t […]

HowTo: Get Around Comcast Port 25 Block with a Postfix ...

This entry was posted in Linux Reference Technology and tagged block blocked Comcast howto port 25 Postfix relay workaround on by (updated 4024 days ago)
Postfix 2.9 Upgrade 6
I’ve previously written a how-to for compiling Postfix from source on a CentOS 5 box. I recently tried following the same steps on a CentOS 6 box, to upgrade from Postfix 2.6.6 which is installed by default. I’m glad to report that the same instructions will work just fine to upgrade […]

Building Postfix 2.10 on RHEL6 / CentOS 6 from Source

This entry was posted in Linux Reference Technology and tagged binaries build CentOS CentOS 6 compile Postfix Postfix 2.6.6 Postfix 2.9 Redhat RHEL RHEL 6 rpm source on by (updated 4331 days ago)
Yahoo and Postfix 26
If you’re getting “temporarily deferred” Postfix log entries when trying to send mail to Yahoo! that look like this: host mta7.am0.yahoodns.net[66.196.118.34] refused to talk to me: 421 4.7.0 [GL01] Message from (xxx.xx.xx.xxx) temporarily deferred - 4.16.50. Please refer to http://postmaster.yahoo.com/errors/postmaster-21.html or status=deferred (host mta7.am0.yahoodns.net[66.196.118.35] said: 451 mta1336.mail.bf1.yahoo.com Resources temporarily unavailable. […]

How-To: Postfix configuration to reduce Yahoo temporary deferrals using Transport ...

This entry was posted in Linux Reference Technology and tagged 420 421 deferral GL01 Postfix refused to talk to me Resources unavailable temporarily status=deferred temporarily deferred Yahoo Yahoo Mail yahoo temporarily deferred on by (updated 3833 days ago)
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One recommended way to help secure your Postfix mail server is enabling TLS (Transport Layer Security) for connections to and from Postfix. You can search for more detailed descriptions of exactly how TLS works, but basically it’s a crypotgraphic protocol that allows connections between systems to remain secure. It relies on a key […]

Configure Postfix TLS with a Free StartSSL Certificate

This entry was posted in Linux Reference Technology and tagged certificate csr free key Postfix self-signed SSL StartSSL TLS on by (updated 3448 days ago)
DKIM Test Message 145
For those who want or need to compile and install OpenDKIM from the source code, you can follow the instructions I wrote in this article. If you’re looking for the fastest and easiest way to get OpenDKIM running on a RedHat or CentOS system, I currently maintain the OpenDKIM package in […]

Installing OpenDKIM RPM via Yum with Postfix or Sendmail (for ...

This entry was posted in Linux Reference Technology and tagged CentOS DKIM dkim-filter dkim-milter dkim-proxy Fedora Linux OpenDKIM opendkim-genkey opendkim-milter opendkim.conf Postfix RHEL rpm sendmail yum yum opendkim on by (updated 3228 days ago)
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A while back, I noticed a recurring error in my maillog that read: postfix/smtp: certificate verification failed for gmail-smtp-in.l.google.com[74.125.53.27]:25: untrusted issuer /C=US/O=Equifax/OU=Equifax Secure Certificate Authority If you’re seeing this too, there’s an easy fix.

Fixing Postfix “certificate verification failed for gmail untrusted issuer” Error ...

This entry was posted in Linux Reference Technology and tagged certificate certificate verification failed Equifax gmail untrusted issuer OpenSSL Postfix SSL Certificate Thawte on by (updated 3833 days ago)
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If you have an email address, then it’s almost certain that you’ve had to type it into at least one online form. And if you’re like most, you’re required to do it on a regular basis. One way to help track whether that email address gets shared (and to be […]

How to use Address Tagging ([email protected]) with Postfix

This entry was posted in Linux Reference Technology and tagged address tag address tagging Postfix recipient delimiter recipient_delimiter SPAM user+tag [email protected] user-tag on by (updated 5023 days ago)
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This is another one of those articles I write mainly so I can reference it later to help me remember how I got something working, but if it helps someone else trying to get Amavis, ClamAV, and SpamAssassin working with Postfix on Fedora, then great!

Tips for installing Amavis-new, ClamAV, and SpamAssassin using Postfix on ...

This entry was posted in Linux Reference Technology and tagged Amavis-new ClamAV Fedora Fedora 12 Fedora Core 12 Postfix SPAM SpamAssassin on by (updated 4947 days ago)
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Before proceeding with this tutorial, and at the risk of possibly overstating what is obvious to some, I want to make three things clear:

How to get DKIM and DomainKeys working with Postfix on ...

This entry was posted in Linux Reference Technology and tagged CentOS CentOS 5 CentOS 5.5 CentOS 5.x dk-milter DKIM DomainKeys DomainKeys Identified Mail OpenDKIM opendkim-milter Postfix RHEL RHEL 5 RHEL 5.5 Sender Policy Framework sendmail signed SPF on by (updated 3833 days ago)
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UPDATE 7/11/15: The following procedure will work on RHEL/CentOS 7, 6, and 5 systems to upgrading from those systems’ default versions to Postfix 3.02. CentOS (a non-commercial clone of RedHat’s RHEL) is my server operating system of choice because it’s extremely stable and widely-used. One of the reasons it’s so stable is […]

Building Postfix on RHEL / CentOS from Source

This entry was posted in Linux Reference Technology and tagged binaries build CentOS CentOS 5 CentOS 5.5 CentOS 5.x CentOS 6 compile Postfix Postfix 2.3.3 Postfix 2.6.6 Postfix 2.8 Postfix 2.9 Redhat RHEL rpm source on by (updated 3440 days ago)
Linux Uptime 180
Update! RPMs and Yum now available. I build and maintain the RPM packages of OpenDKIM for RHEL/CentOS and Fedora, which are available with Yum. For a much quicker and easier way to install OpenDKIM, read this. Of course, if you still prefer to go old-skool and compile your own binaries […]

How to get DKIM (DomainKeys Identified Mail) working with Postfix ...

This entry was posted in Linux Reference Technology and tagged 20209 CentOS CentOS 5 CentOS 5.5 DKIM dkim-filter dkim-milter dkim-proxy DomainKeys DomainKeys Identified Mail GoDaddy OpenDKIM opendkim-genkey opendkim-milter opendkim.conf Postfix RHEL RHEL 5 RHEL 5.5 Sender Policy Framework sendmail signed SPF on by (updated 4023 days ago)