Remember when ISPs used to determine which email was spam based on message content, like using "free" in the subject line? These days, they pay more attention to who you are than to what you say. Building up your sender reputation takes time and effort, but destroying it can happen in the blink of an eye. Here are four ways to get banished from the inbox.

1. Using Old or Purchased Lists

This is a common culprit when companies lose their email standing overnight. That's because both types of lists negatively affect two of the most common metrics ISPs use when trying to figure out what to let through and what to block: bounce rates and email spam-complaint rates.

Think twice before deploying a list that hasn't been touched in more than 12 months. The list could be filled with hard bounces – email addresses that are no longer active. As for the addresses that are still viable, you haven't contacted them in so long, they may not even remember who you are. That means those recipients are exponentially more likely to hit the spam button.

Purchased or rented lists can be even more perilous. Even if your list broker assures you that you're buying an "opt-in list," check the fine print, if you can find any. The subscribers may have said yes to somebody, but that somebody wasn't you. Email spam complaints are guaranteed.

You're also at risk of sending to "spam-trap addresses," email addresses posted to the Web for the specific purpose of catching spammers. You see, the CAN-SPAM act makes it illegal to "scrape" or copy email addresses from Web sites and add them to mailing lists. Many purchased lists are chock full of these illegal contacts, and when your message goes out to them, you can quickly find yourself on multiple blacklists even though you didn't do the scraping.

For these reasons, we don't recommend resurrecting dormant house lists, or buying or renting email lists. But if you proceed with these lists anyway, at the very least, remove obvious illegitimate emails like This e-mail address is being protected from spambots. You need JavaScript enabled to view it.  or This e-mail address is being protected from spambots. You need JavaScript enabled to view it.  before hitting the send button.

2. Having a Shared IP Address

The computer server that sends your email marketing campaigns has a unique IP address, and it's the email equivalent of a Social Security number or passport. The problem is, unlike a unique government ID that is issued to you and you alone, the IP address applies to any and every email coming out of that server, even if different companies are sending those messages.

You could be sharing an IP address with a few companies or a few hundred companies, depending on the server-farm setup of your email marketing service provider. You won't know who these other companies are, and you have absolutely no control over what they do. Yet, your marketing reputation will be only as good as the worst company you share the IP with.

Many ESPs offer dedicated IP addresses for an additional fee. A dedicated IP means that only your company gets to send messages from that particular computer, giving you complete control over your email reputation. If protecting email deliverability is important to you, a dedicated IP is a worthwhile investment.

3. Sending Nonauthenticated Email

ISPs use a variety of authentication protocols to confirm that you are who you say you are, such as SPF, Sender ID and DomainKeys. These technical protocols allow ISPs to verify that you're a legitimate mailer, not someone engaging in spoofing, phishing or other illegal activities.

Most email-marketing software provides support for these various protocols, but authentication generally isn't something that you or your ESP can activate without help. Someone on the technical side of your business, such as a webmaster or IT person, needs to spend a few minutes updating DNS records that associate your company's Web properties with specific IP addresses.

Check your ESP's user guide for instructions and verify that your "From" addresses are properly authenticated, because ISPs are less likely to deliver mail from those that aren't.

4. Neglecting to Send a Welcome Email

Sending a welcome email whenever new subscribers join your list is more than a polite courtesy, it's actually a method of preventing future spam complaints.

A good welcome email reminds your new subscribers of who you are, why they joined and what they can expect from you in terms of message frequency, content and branding. It's also an opportunity to build goodwill by including a coupon or giveaway as a thank you for subscribing.

Promptly sending this initial welcome email increases the likelihood that subscribers will recognize you when your production email arrives days or weeks later. And knowing who you are makes all the difference between reading your email and reporting it as spam.

There's also one last deliverability benefit to your welcome email. You can use it to encourage readers to take the one step that often fast-tracks your messages to their inboxes: adding your email address to their address books or safe-sender lists.

Read How Valuable is Your Email? for more on the components of a good welcome email, email list management and email marketing tips.

Protect Your Email Reputation

As you can see, a few bad moves can easily ruin your email reputation. You can improve email deliverability just by being mindful of your lists, using a dedicated IP, authenticating your email and welcoming new subscribers. All four go a long way toward protecting one of your company's most valuable assets: its good name. 

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About The Author:

David Fowler is the director of email strategy, deliverability and privacy compliance for Lyris. He consults with email marketers to help them get better results from their email programs.

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