Email marketing is one of the most dependable tactics in the marketer's playbook. Flashy, new marketing channels come and go every year, many of them promising to yield impressive ROI, but few of them can actually compete with the tried-and-true approach of email.

Email is relatively simple to use, and it delivers great ROI. So it's a no-brainer that companies ranging from financial services to retail would prioritize email marketing as a top contributor to their strategy.

Although easy to use, email is difficult to master if you don't act on insights that can help deliver impact. And, often, the result of that neglect is beautiful emails, with tempting calls to action, but they get marked as spam and don't make it to the recipient's inbox.

As we enter a new year and a new chapter in digital marketing, it's imperative that your email campaigns reach their intended destination. Accordingly, here are five best-practices to boost and maintain email deliverability in 2020.

1. Don't ambush your mailing lists during peak times. Do gradually increase email outreach ahead of major seasons.

It's tempting to blast out as many emails as possible to get your customers' attention and to drown out the competition. But by doing that you risk not only turning off your customer but also having your campaigns flagged as spam, or—worse—you can be blacklisted by Internet service providers (ISPs), which could dent your deliverability rates.

You'll be better off setting a cadence of personalized messages months in advance of an important season for your industry. For instance, if you're a travel company wanting to reach spring-breakers, start by gradually sending emails that play up what's in store for your customers months in advance, to start build momentum as the season approaches.

That gradual approach gives you the ability to build awareness, share brand news with new and existing customers who are the most likely to engage with it, and react to metrics in real-time to maximize conversions.

2. Don't send the same email to everyone on your lists. Do practice audience segmentation.

Email experts never recommend the "spray and pray" method because it's a surefire way to get subscribers to quickly unsubscribe or flag your messages as spam. And you can't blame them—because email marketers should know better than to send an email about new knitting needles to a customer whose brand engagement suggests an interest in action sports.

Use the data available to your marketing team to send targeted, personalized email offers like a birthday deal or a heads-up that an out of stock item a subscriber favorited is back on the shelves. That personalized approach will increase your deliverability rates, and you can also expect to see conversion rates go up since you're providing what customers need right when they need it.

3. Don't suddenly go rogue. Do keep up what's working.

Though you're often taught that high risk equals high reward, don't take a risk right before your most profitable times of year.

Sure, you may see a surge in sales by pushing out an untested campaign to your traditional audience. But if it doesn't pan out, your ROI may plummet to depths it likely wouldn't have reached had you experimented during safer seasons.

Instead, look at all of your past campaigns; identify what delivery, messaging, and creative tactics have produced the best results—and stick to your brands' best-practices during crunch times.

4. Don't keep emailing to subscribers who aren't engaged. Do practice list hygiene.

List hygiene—regularly cleaning out inactive subscribers—is one of the most important things you can do to maintain the health of your email campaigns all year round.

Persistently emailing disengaged subscribers can have devastating effects on your email reputation. Instead, analyze how often the customer responds and adjust accordingly. Is the customer responding less often? Send fewer emails. This approach will pay dividends in the long run for your email marketing ROI.

5. Don't forget about the competition. Do craft compelling subject lines.

If you're in a particularly crowded industry, check in on the emails your rivals are sending and adjust your strategy accordingly to turn customers' attention your way. An effective way to do that is to master the art of the subject line.

To a customer, your subject line is like a handshake: Too weak, and you risk their scrolling past your email; too strong, and you risk their clicking "mark as spam." Better to be friendly, yet direct, by giving them a factual peek into what's inside your message that they'll find worthwhile.

Is it a time-sensitive price drop on a favorite item? Say that, and don't be afraid to get creative when you do. Just make sure your creativity doesn't veer into ambiguity, because contrary to popular belief, vague subject lines like "Have a second?" piques your subscribers anxiety, not curiosity.

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In 2020, the stakes will be high for marketers to make the most out of marketing budgets and deliver tangible results for their companies. Consequently, instead of jumping on the bandwagon of miscellaneous emerging marketing trends that have yet to prove their mettle, master the basics of proven methods like email.

By properly leveraging one of the most established tactics in the marketer's toolbox and incorporating the best-practices outlined in this article, you'll be able to increase email ROI for your company and maintain high inbox reputation with your customers.