Three authentication systems that can help boost email delivery rates

If you send a reasonable volume of email, you've probably experienced the frustration of being told by some of the intended recipients that they never got your messages.

As service providers have implemented more stringent spam policies, legitimate email senders find that their emails often become collateral damage in the "War on Spam."

Fortunately, there are some simple things you can do that will usually help boost your email delivery rates - especially on popular email services like Hotmail and Yahoo.

Here are some free email authentication systems that I recommend to all of my clients.

• DomainKeys Identified Mail (DKIM) adds a digital signature to the header of yours emails that enables the recipient's email server to verify that the email was really sent by your server. DKIM was designed by a Yahoo employee and Yahoo is one of the email providers that uses DKIM to validate the origin of emails received by its users.
• Sender Policy Framework (SPF) allows you to add a special DNS record to your domain name that specifies what servers are allowed to send email using your domain name. An email server receiving an email can then check the sender's SPF record to verify that the server the email was sent from was authorized by you to send the email. SPF is widely used by popular online services, mail transfer agents (MTAs) and anti-spam applications/services.
• SenderID is essentially SPF with a few additions. It is implemented by Microsoft (which owns Hotmail) so it too is well worth implementing. Most of the websites linked to above have information about setting up these systems and a qualified server administrator should have little difficulty in doing so.

One note - implementing SPF, SenderID and DomainKeys does not guarantee that your emails will be delivered, and does not eliminate the need to implement other best practices that minimize the risk of your emails being mistakenly identified as spam.

That said, in today's environment, not using these systems may unnecessarily make it more difficult for your emails to be received. If email delivery rates are important to you, you'll want to make sure that DKIM, SPF and SenderID become your friends and not your enemies.