Remember “Things That Make You Go Hmmm?” The catchy tune has nothing to do with email marketing. Nevertheless, please consider it the theme song for this post, which looks at four practices that email marketers should think twice about (an audible “hmmm” is optional, of course). They are:

1. Resending emails

It seems logical enough. Your message didn’t get the results you wanted, so why not simply send it again? But it turns out that may not be a great idea.The central problem with resending and reusing old emails is that it’s simply not a sustainable approach,” writes Scott Heimes at Marketing Land.

“For one, you risk doubling unsubscribes from what is essentially a single email.” The practice can also put your messages “in the sights of ISPs, spam filters and blacklists” and contribute to “email fatigue,” Heimes argues.If you determine that a message is so important that it absolutely needs to be resent, be sure to tweak its subject line, send it at a different time and track the resulting unsubscribes against conversions, advises Kelly Newbery at Vision6.

2. Purchasing or renting email lists

You can’t do email marketing without email lists, so why not simply buy or rent them?

Don’t do it, writes Corey Wainwright on the HubSpot blog. “If someone actually had a good email list, they’d keep it to themselves because they don’t want to see the value of those email addresses diminished by letting other people get their hands on it,” he writes. “Think about it – would you sell or share the email addresses of those who have voluntarily opted in to receive email from you? I didn’t think so.”

Downsides to purchasing or renting lists include that fact that reputable email marketing vendors will not work with them, recipients are likely to mark them as spam, your delivery rates will suffer, and you will put your reputation at risk, Wainwright says.

Work to grow your own opt-in lists instead. Need ideas for doing that? Here are 25.

3. Sending everyone the same message

“Rather than taking the time to craft variations of an email based on your customers’ wants, it is comparatively quicker and easier to compose one general-sounding email with which to blast your entire contact list,” writes Phrasee. “But what seems like a time-saving tactic is actually a big mistake.”The alternative is, of course, list segmentation, which is likely to boost your open rates, reduce unsubscribes and, most important, drive revenue.

“Email marketing segmentation is the art of thinking in groups,” writes Jordie van Rijn at emailmonday. “You have to realize that your email list consists of different kind of people, with different behavior, profiles, and interests. But if your subscribers are so different, why treat them all the same?”

Need a guide to effective list segmentation? Here you go.

4. Taking subject lines for granted

You’ve spent countless hours planning your campaign and developing content. But if you are ready to hit “send” and have not put effort into crafting a strategic, compelling subject line, it’s time to hit the “pause” button.

While the subject line is often left until the last minute and doesn’t have a lot of thought put into it, almost half of all email recipients decide whether or not to open an email based on the subject line alone,” writes Jomel Alos on our blog. “That’s a 50% chance of your lead-building email efforts going to waste if you don’t pay attention to your subject lines.”

Jomel offers six tips for crafting successful subject lines: personalize them, use numbers and lists, use emojis, use short or even one-word subject lines, be careful with punctuation marks, and avoid using “FOMO” terms like “last chance” and “ends today.”

5. Thinking “personalization” means simply using a first name

Personalization has come a long way in a very short time. The possibilities represented by innovative “moment of open” contextual practices seem limited only by imagination.

But for some email marketers, “personalization” still equates to using the recipient’s name in the message.

“Hello {{contact.firstname}} is the most clichéd start to an email that every marketer is accustomed to using in their marketing emails,” writes Kevin George at Email Monks. “It is important to treat your subscribers as a valued asset. One of the best ways to do so is to make your subscriber feel like an integral part of your brand rather than being just a name on your mailing list.”

For more on personalization, check out the recording of our The State of Email Marketing Personalization in 2017 webinar.