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How to Avoid Deliverability Pitfalls: 10 Ways to Dodge Spam Traps, Blacklists, and Other Perils

Safely arriving into your customer's inbox is one of an email marketer's primary goals. Often, however, it's also an uncertainty negatively impacting your email program's success and performance. Don't let it happen to you

At least 2-3 times per day, clients ask us: why aren’t messages delivered to the inbox? Why do they see a decreasing trend in open rates? How can they ensure subscribers see the emails sent to their inbox?

To help answer these questions and provide easy-to-execute, actionable tips that put you in control of where your messages get delivered, let’s first note 3 main areas that impact deliverability: identification, reputation, and content.

Identification is how you can prove to each of the ISPs that you are who you say you are when you send an email. Typically, you accomplish this by successfully configuring, implementing, and validating your DNS records, which use DomainKeys Identified Mail, almost like a background check.

Reputation is a unique score given by each ISP, and it denotes your trustworthiness. Having subscribers engage with your emails is the best way to boost your score and show you’re a trusted sender. For this reason, making sure your messages are relevant, personalized, and timely can help increase engagement and reputation.

And finally, the content of your messages plays a vital role in deliverability. Is it relevant to the recipient? Does it follow best practices, like including an unsubscribe link in marketing messages? Remember, if your recipient doesn’t feel the message makes sense or isn’t relevant, they may mark it as spam – which impacts deliverability over time.

With that in mind, here are 10 quick tips you can implement today to help optimize your email program and avoid common deliverability pitfalls.

#1 Clean your list

You may have heard us say this once (or a few times – especially during our IP Warm-Up Kick-Off call), but subscribers who haven’t engaged in a while are more likely to bounce or worse yet – their address may now be a spam trap or honeypot. These are dormant addresses that ISPs then disable and after a while, reactivate. Once reactivated, they (or a 3rd party like Spamhaus) monitor the addresses with the understanding that anyone still sending to the address is likely a spammer, as they’re not following sending best practices. To avoid falling into one of these traps, regularly cleanse your list or validate addresses with a lapse in engagement of 12+ months for potential threats.

#2 Segment your audiences

You’re likely to send to a spam trap or honeypot if you continuously mail to subscribers who show significant engagement lapses or registered 12+ months ago but never opened an email. It’s a good idea to add attributes to your target groups, suppressing addresses based on engagement. While we recommend avoiding repeat sending to those with a lapse of 6+ months, compare your data and group sizes between 6+ and 12+ lapses in engagement to find a target group size you’re comfortable with and inbox delivery performance that proves successful.

#3 Don’t buy your lists

This may seem obvious but never buy an email list. Some marketers continue to use purchased lists to send their email promotions, thus taking a considerable risk. When you buy or rent a list, you don’t know how the addresses were collected or the opt-in process that was used. There’s a chance there’s a spam trap or two in your list. Moreover, you can expect a large percentage of addresses to mark you as spam since they didn’t personally subscribe to receive your content and may feel it’s not relevant to them.

#4 Don’t wait. Authenticate

Email authentication is a necessary practice that helps block fraudulent phishing and spammers from sending messages to your customers through linking your IP address to your domain. When you receive your DNS records from Optimove, don’t wait to implement them. Make sure they’re correctly configured and verified before you start to send your campaigns. Otherwise, you may find your IP listed on several blacklists before you complete your warm-up.

#5 Don’t hide your Unsubscribe

The unsubscribe link is required by the CAN-SPAM Act; it is a compliance requirement. But when it comes to avoiding significant deliverability and inboxing issues, giving subscribers the ability to opt-out vs. complain (i.e., identify your message as spam), gives you more leverage. Make sure your unsubscribe is easy to find and consider giving subscribers the option of opting down vs. opting out if you believe frequency causes friction. Sometimes spam complaints, which ISPs use to determine your reputation, occur because it was easier to find how to click “spam” than it was to opt-out.

#6 Engage your subscribers, don’t overwhelm them

Sending that 50% off discount today, a reminder tomorrow and the next day, and then a “Don’t Forget” the day after followed by a few “Only a Few Hours Left” urgency messages… is a practice sure to leave a few subscribers hitting the spam button or not opening at all. Focus on frequency & segmentation strategy that looks at who’s engaged, who’s converted, and who’s the right recipient for the right message at the right time.

#7 Ask, and you shall receive

Sometimes, avoiding the junk or spam folder is as simple as asking. Whatever the case may be, adding whitelist instructions so that subscribers can add you to their “safe senders list” keeps your messages landing in their inbox – even when they don’t always open or click through on them. Whitelisting instructions vary from ISP to ISP and email client to email client, so be sure you’re providing all appropriate instructions. But regardless – it’s a great idea to include small text at the top of your messages asking subscribers to add you and why (i.e., “To continue receiving great content like this…”).

#8 Avoid attachments

Sure, you may have an excellent white paper you want to get in front of your subscribers or a cool file you want to share. Still, when sent as an attachment, ISPs see it as a red flag and will almost immediately redirect your message to spam or block it altogether. In some cases, it may be due to the overall file size, and in others, it’s often used to hide viruses and malware. In either case, sending attachments in your email negatively impacts on inboxing. While this may not result in blacklisting, it does result in fewer messages making their way to your audience. There’s a simple solution: don’t send attachments. Instead, consider linking subscribers to a unique landing page where they can download the content.

#9 The double opt-in

This method ensures only valid and engaged subscribers are added to your mailing list, capturing typos, spam traps, and more when sending the opt-in confirmation email that the subscriber must click on to confirm their subscription request. Since it means your email list include only recipients who have explicitly asked to receive your messages, you’re going to see higher open and click rates, and better inboxing, while gaining a better reputation as a sender overall.

#10 Roll out the Welcome mat

Use your Welcome message as more than just a confirmation email. It’s your chance to set the tone for what’s to come – what you’ll be sharing with your recipients, how you hope they’ll respond, maybe even how often they can expect to hear from you. If your Welcome message says you’ll be sending informative tips once a week, but you start sending offers and discounts every day, you’ve tarnished your image in your recipients’ eyes. They’re likely to mark you as spam or stop engaging – which lowers your reputation score.


The critical thing to remember when it comes to getting your messages into your customer’s inboxes and avoiding blacklists and spam traps is that you’re in control. The sending practices and strategies you use today impact the place your messages land tomorrow and in the future.

Moreover, blacklisting happens to a lot of marketers and well-respected brands. When it does, or when you see a significant drop in engagement, contact your Deliverability Support Team at Optimove. We’re experts at troubleshooting the cause and working with you, the ISPs and public blacklists to quickly and efficiently remove you so your messages will get into your customers’ inboxes again.

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Jonathan Inbar

Jonathan Inbar is a marketing data scientist on Optimove’s Strategic Services team. As a marketing data scientist, Jonathan leverages his extensive experience with building predictive models and generating data-driven marketing insights to consult with clients and help them optimize their CRM strategy and tactics. Jonathan holds a BSc in Industrial Engineering and Management, specializing in Information Systems, and two specialization certificates in Machine Learning from Duke University and the University of Washington.

Dana Shirlen

Dana Shirlen leads Optimove’s internal email marketing agency as Director of Email Marketing. Dana has over 15 years managing the email marketing strategies of many recognizable global B2C and B2B brands. As the Director of Email Marketing, Dana is bridging the gap for Optimove’s customers in providing a data-driven marketing plan and timely implementation grounded in best practices, targeted content and visually engaging design. Prior to her role at Optimove, Dana managed the CRM and email marketing strategies for enterprise clients at Tinuiti. Dana holds a BS from Ohio University, with a major in Advertising Management and concentrations in both marketing and creative writing.