This is a simple mechanism, using DNS to certify that email from your domain comes from authorized servers. This is accomplished by adding a DNS record to identify the servers from which you send legitimate email. Emails sent from other servers MAY then be assumed as forged (SPAM) and blocked by the receiving email server.
NOTE: This can be easily spoofed, as such it should be a portion of your email security strategy, look into DKIM and DMARC too!
One thing that I initially did not understand… if you are supporting IPv6 and IPv4, you should merge your records onto a single DNS TXT entry:
example.com TXT v=spf1 a mx ip4:xxx.xxx.xxx.xxx ip6:xxxx:x:xxx:xxxx:xxx:xxxx:xxxx:xxx -all
I’ve found New Relic to be a great free addition to my suite of tools for server monitoring and alerting as I shifted to a DevOps support environment.
Installation is very fast an simple once you’ve created a free accound. Paid options are available and allow for more features.
You will need to record/save YOUR_LICENSE_KEY from your account for step 5 below.
sudo sh -c 'echo deb http://apt.newrelic.com/debian/ newrelic non-free > /etc/apt/sources.list.d/newrelic.list'
wget -O- https://download.newrelic.com/548C16BF.gpg | sudo apt-key add -
sudo apt-get update
sudo apt-get install newrelic-sysmond
sudo nrsysmond-config --set license_key=YOUR_LICENSE_KEY
sudo /etc/init.d/newrelic-sysmond start
You are done! Within a few minutes you should start seeing data on your consoles at the New Relic website.
Website network performance is usually a very complicated process. Over the years, I’ve outlined many development techniques that can be used toward this goal. I’d heard about mod_pagespeed for some time, but never had the opportunity to experiment with it until recently. My first impression is that it is a VERY EASY means to gain performance improvements without reworking your existing website to implement techniques for establishing far-future expires, cache-busting, minification and static file merging.
Out of the box, most common techniques are automatically applied to your assets and a local server cache is created to utilize them.
Default installation is trivial:
- Download the latest version for your server architecture:
sudo dpkg -i mod-pagespeed-*.deb
sudo apt-get -f install
sudo service apache2 restart
NOTE: Using tools like Firebug will enable you to see an HTTP Header indicating the version being used for your requests.
If you need to modify configuration from the default:
sudo vi /etc/apache2/mods-available/pagespeed.conf
For VirtualDomains, you can selectively enable and disable PageSpeed and many of it’s settings in your appropriate configuration files with:
?ModPagespeed=off to your URL will disable functions for that request.
<script defer="defer" src="example.js"></script>
NOTE: Do not use defer for external scripts that might depend on each other if you need to support MSIE9 and earlier.