In love and in marketing, you have to learn to admit when a relationship isn't working—especially when the email subscribers you're attempting to woo are hurting your performance numbers.

Email is a great medium for connecting with leads and customers. But when your list becomes bloated with bad addresses and inactive subscribers, it's time to clean house.

Otherwise, you're merely sending messages to bots and people who don't want to hear from you, and you're also damaging your engagement rates and deliverability rates, making it harder for you to reach the subscribers who do want to hear from you.

You're even risking getting blocked and blacklisted.

So let's look at the four types of offending addresses and how to deal with each of them effectively.

1. Invalid Email Addresses

Invalid addresses are unmailable: They don't match any existing email accounts. You end up with them because sometimes people submit their contact information with typos. Others purposefully enter fake email addresses because they're annoyed that they have to provide one to access a site, and they'll give addresses such as "nothanks@no.com" or "nope@nope.com" to avoid unwanted emails.

As clever as that tactic may be, it results in hard bounces for marketers who send messages to those fake addresses. Inbox providers monitor what percentage of a sender's email addresses hard-bounce, and if the number goes above 2% or so, they can block or junk the sender's messages.

Consider using an email validation service, and ensure your email service provider is immediately removing any of your addresses that hard-bounce.

Scrutinize any acquisition sources that produce a lot of problematic addresses. For instance, addresses collected via pen and paper often hard-bounce because of transcription errors, so consider using tablets to collect signups to reduce those mistakes.

2. Spam Traps

All spam traps pose risks to marketers, but the most harmful are pristine spam traps—email addresses created by inbox providers and blacklisting organizations to identify spammers. Inbox providers hide those addresses on Web pages; the addresses then get picked up by spammers who use harvesting software to scrape the data.

Because the addresses never circulate legitimately, inbox providers and blacklisting groups know that any sender who sends emails to these accounts either harvested the information or bought email lists from someone who did.

In some cases, having just one spam trap on your email list is enough to get you blocked or blacklisted.

Unfortunately, spam traps are difficult to combat because they look just like all of the valid ones on your list. If your deliverability plunges and you suspect you've picked up a spam trap, your only recourse is to purge all of the email addresses you collected at around the time your deliverability tanked, and/or those you collected through the same method.

3. Role-based Email Addresses

Departmental addresses, such as "sales@company.com" or "events@company.com," should be taken off your list. Businesses typically use those to accept and respond to questions from customers and prospects, not subscribe to newsletters.

Even if a role address were actually used to subscribe, there would be risks because multiple people use those accounts. The person who signed up for your newsletter might forget to tell the rest of the team, and someone else on the team might mark your email as spam.

Because they're often posted on company websites, role-based email addresses also frequently end up on spammers' lists, so inbox providers frown upon senders who message too many such accounts. Err on the side of safety, and remove all emails of this type from your database.

Check with your email service provider to see whether list hygiene tools are included in its software that remove these email addresses. If not, there are plenty of email hygiene services you can integrate into your processes to do the job.

4. Inactive Subscribers

Inactive subscribers fall into two categories: never-actives and chronic inactives. Never-actives are new subscribers who haven't engaged with any of your emails; chronic inactives have opened and clicked through your messages in the past, but they have since ignored them for several months or longer.

In addition to considering negative metrics such as spam complaints and hard-bounce rates, inbox providers monitor positive metrics, including open rates and other engagement indicators. When lots of inactive subscribers leave your emails unopened, they drag down your engagement numbers. And once those rates get too low, inbox providers will begin blocking and junking your messages.

Unlike the other accounts (types of email addresses) I've mentioned in this article, inactive subscribers are worth saving—within reason.

Send never-actives a one-time re-permission email that asks them to confirm their interest in hearing from you. Include a button they must click to stay on your list. If they don't click, remove them from your active list.

Chronic inactives require a bit more strategy. Generally speaking, you don't want to keep them on your list for more than 25 months. If you email to your list more than once a week, the cut-off for chronic inactives might be a year or less. At that frequency, their poor open rates could hurt your deliverability metrics more quickly. You may want to establish tiered cut-offs for current and lapsed customers separately from non-customers.

Before you reach those deactivation periods, however, deploy re-engagement campaigns to keep them active. Offer steep discounts to get them back on your site or request that they update their preferences. Protect your engagement metrics by decreasing the number of emails you send to them during the re-engagement period; then, if they don't re-engage, send a series of re-permission requests before taking them off your active email list.

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Building a productive email list requires solid permission practices and a watchful eye on the email addresses that are making it onto your list. But it also requires you to monitor your list for inactives so you can effectively serve the people you know want to hear from you.