The success of an email marketing program is based on a range of factors, including eye-catching subject lines, valuable offers, quality copy, etc. But there’s one factor that you must consider before you even begin to compose copy: the cleanliness of your email list.

Even if your list is entirely built on valid opt-ins, you are at risk of being branded a “spammer” if you don’t practice proper email hygiene.

Here is why:

1) ISPs base complaint rates on active subscribers, not total subscribers.

If your list is loaded with inactive emails, you don’t have a sense of your true complaint rate. While many marketers just look at total complaints over total list size, ISPs (internet service providers) are actually looking at total complaints over number of active email users.

Suppose your email to 1,000 addresses arrives at 400 inboxes and generates 10 complaints. A marketer might think their complaint rate is only 1% (10 / 1,000); however an ISP will compute a rate of 2.5% (10 / 400) -- a rate that is high enough to get you blocked by certain ISPs.

ISPs started caring about active users when they caught on to a loophole that spammers were exploiting. In an attempt to game the system, spammers started to stuff their lists with inactive email addresses. They did this because inactive accounts will never click the spam button, and therefore, the total spam complaints would stay artificially low. Sneaky!

2) Expired email addresses turn into spam traps.

Since spammers tend to buy and steal lists, ISPs resort to yet another method to track them down: ISPs mark abandoned email addresses as spam traps. This means that, even if you acquired emails in a legitimate manner, the abandoned addresses may have morphed into spam traps. Hitting even just one spam trap can cause deliverability problems.

3) Expired email addresses turn into unknown accounts.

When an ISP sees that you’re sending to a large number of unknown accounts, once again, they will suspect that you are a spammer. In fact, if you hit unknown accounts at a rate higher that 5%, it is very likely they will send your emails directly to the spam folder or will block you altogether.

The Solution: Email List Hygiene

The solution to all three of these problems is to regularly clean up your email list by removing those addresses that are no longer engaged. You can identify these addresses with metrics such as opens, clicks, or website activity. Aside from all of the money you will save from sending less email, you will achieve higher deliverability and a stellar reputation with the ISP gods!