1. Habeas.com
Secure email management with Habeas will ensure accurate email delivery through monitoring email authentication and delivery of emails from legitimate senders. Avoid blacklists with Habeas email solutions.
http://www.habeas.com

2. Validator.w3.org
W3C's easy-to-use HTML validation service, based on an SGML parser.
http://validator.w3.org

3. Spamassassin.apache.org Tests Page
The Apache SpamAssassin Project - The Powerful #1 Open-Source Spam Filter
http://spamassassin.apache.org/tests.html

4. Lyris.com Products Emailadvisor Page
Lyris, Inc. is the leading provider of internet marketing tools for marketers at mid-size businesses, including email marketing, web analytics, ppc management, web content management and email deliverability monitoring.
http://www.lyris.com/products/emailadvisor

5. Microsoft.com Wizard Default Page
This four-step wizard will guide you through the process of creating a new SPF record for your DNS domain. You should add this DNS record to your domain's DNS configuration.
http://www.microsoft.com/mscorp/safety/content/te~

6. Old.openspf.org Wizard Page
The SPF Setup Wizard - Most domains send outbound mail through a relatively small number of servers. Domains should describe that set of servers in an SPF record in their DNS.
http://old.openspf.org/wizard.html

7. Domainkeys.sourceforge.net
DomainKey Implementor's Tools and Library for email servers & clients
http://domainkeys.sourceforge.net

8. Trustedsource.org
TrustedSource is the industry's most complete Internet reputation system.
http://www.trustedsource.org

9. Aweber.com
Learn About the Most Reliable, Easiest, Cost Effective Tool to Capture Visitor Sign Ups, Send Unlimited Follow Ups and Newsletters Increasing Your Profits.
http://www.aweber.com

10. Returnpath.net Senderscore Page
The days of "send first, ask questions later" are gone. Email marketing is no longer the Wild West.
http://www.returnpath.net/senderscore

11. Member.dnsstuff.com Pages Dnsreport Page
Tools and Reports for DNS Domain name Servers and Information System Networks.
http://member.dnsstuff.com/pages/dnsreport.php

12. Abuse.net Relay Page
Mail relay testing - We offer an experimental mail relay testing service. It runs in two modes: Anonymous mode sends commands to the server to be tested but doesn't actually send any mail.
http://www.abuse.net/relay.html

13. Emaillabs.com Best_practices Page
A collection of email marketing best practice and quick tips to help marketers optimize their email marketing programs.
http://www.emaillabs.com/best_practices

14. Domainkeys.sourceforge.net Selectorcheck Page
DomainKey Selector Record Tester
http://domainkeys.sourceforge.net/selectorcheck.h~

15. Dnsstuff.com
DNSstuff: On-demand DNS and network tools to analyze, diagnose and monitor a domain or IP address.
http://www.dnsstuff.com