Email Deliverability problems begin to happen during the time in your startups life when your organization starts changing from that of a child company to that of an adult company. While there’s no “right” time for Email Deliverability optimization to begin, web startups usually start a little earlier than brick and mortar startups—usually between 2 and 6 months of age. Deliverability Optimization for brick-and-mortar startups usually begins at about 10 to 14 months of age.

So, here you are, cruising around the internet, looking for a way to configure your startup’s email system to avoid all those nasty spam traps out there. Your startup is getting interested in e-mailing your users. It’s okay, and it’s natural. Lucky for you, I’ve just done a gaggle of research and am posting what I’ve found here, on Owocki dot com:

Email Deliverability is all about reputation. Specifically, the reputation of the sending computer or ISP:

1. Get a Dedicated IP Address. If other people are sending email from your IP Address, then they affect your reputation. Fair or not, that’s the way it is. Contact your hosting provider to get your own dedicated IP.
2. Implement SPF. SPF is a way of verifying that mail came from your domain by whitelisting different IP addresses to send mail on your behalf. More info at the SPF Wikipedia article.
3. Cache your SPF with Sender ID. Do that via this form.
4. Implement DKIM. DKIM is a way of verifying that your email came from an authorized source. You’ll need to integrate it with Sendmail (or whatever MTA is configured on your host). More info here.
5. Verify your Mail Transfer Agent is not set up as an open relay. Do that here.
6. Implement Reverse DNS. More info here.
7. Process Email Bounces – Remove those users from your email list. List Quality is very important. The more spam complaints / bounced emails your email system generates, the more your reputation is hurt.
8. Add emails to your subscription list only via an opt-in or double opt-in process.

After you’ve done all of the above,

1. Use a service like Return Path to monitor your reputation.
2. You’ll also want to look into getting your domain white listed with major ISPs.

Thanks to Return Path for laying out the most important parts of Email Deliverability to the 2008 Techstars.

UPDATE 2013 : Check out SendGrid.com – They can solve many of these problems out of the box.