Zerobounce

At some point in their email marketing experience, many organizations will run into deliverability challenges. If you’re seeing a steep drop in engagement or find your campaigns in the spam folder, you may be experiencing low deliverability. In this article, we’ll cover basic deliverability troubleshooting for email marketers.

What is Deliverability?

In layman’s terms, deliverability describes the likelihood your emails will end up in spam. 

Emails with high deliverability are likely to make it to the inbox, while emails with low deliverability (or deliverability issues) are likely to get flagged as spam. Deliverability is influenced by several factors, which can make it challenging to identify a singular reason emails start going to spam.

However, there are a few common culprits an email marketer can look for in their domains, account setup, audience, and campaign creation practices.

Why Emails Go to Spam

There are a few common reasons emails end up in spam, including:

1. Lack of domain authentication
2. Misconfigured DMARC, SPF, or DKIM Records
3. Blacklisted domain
4. Invalid addresses or spamtraps in the audience
5. Spam reports from recipients
6. Irregular send frequency
7. Spammy email content
8. Large file sizes in emails

In the following sections, we’ll cover reasons why emails commonly end up in spam, as well as a few other tips & tricks to address deliverability.

Authenticate Domain Through Your ESP

Most ESPs (Mailchimp, Klaviyo, etc.) provide a tool to authenticate your domain. Authenticating your domain means adding a handful of records to your DNS in order to prove that you have ownership of the domain and are legitimately sending email through the ESP.

Authenticate your domain in Mailchimp: Log into both Mailchimp and your domain host (Google Domains, Bluehost, GoDaddy, etc.). In Mailchimp, click on your profile picture, choose “Account & Billing,” then choose “Domains.” Mailchimp provides step-by-step instructions on how to add the appropriate records to your DNS.

Authenticate your domain in Klaviyo: Log into both Klaviyo and your domain host (Google Domains, Bluehost, GoDaddy, etc.). In Klaviyo, click on your company name on the lower right corner of the page, then choose “Settings.” Go to the “Email” tab and click “Sending Domains.” Input your sending domain, and Klaviyo will provide prompts to walk you through the process.

Configure SPF, DKIM, and DMARC

Even if you’ve authenticated your domain through an ESP, you may still run into domain configuration issues. The key DNS records for email deliverability are:

• SPF: Lists the IP addresses permitted to send emails using your domain.
• DKIM: Verifies emails as legitimate using encrypted hash codes. Emails received are checked against what was originally sent to rule out tampering. Here’s how it works.
• DMARC: Builds on SPF & DKIM to define how email receivers should respond to non-compliant mail. Learn more on DMARC.org.

How do you know if there’s an issue with your SPF, DKIM, or DMARC records? We recommend a tool like MXToolbox or Dmarcly. Google and Yahoo launched new sender requirements in 2024, so it may be worth double-checking if you haven’t recently.

If there are severe problems with your DNS record configuration, a generalized email marketing expert may be unable to resolve them. Consider working with a DNS specialist who can analyze and correct your records.

Check the Blacklists

Some emails land in spam because the sending domain has been blacklisted. This means the sender’s IP address or domain has been added to a list of known spammers. While being blacklisted can be frustrating, it doesn’t have to spell the end for your email marketing program.

To remove your email from a blacklist, you’ll have to take the following steps:

1. Use a blacklist checker to identify which list you’ve been added to
2. Notify the blacklist database and receive their report
3. Clear up any problems or suspected issues
4. Wait for your email to be removed from the list

Some blacklists are harder to escape than others. Check out this guide from Mailchimp for more information on how blacklisting works and why some blacklists (like SenderScore) are stricter than others.

As a first step, you can pull up a blacklist report for your domain using any of the blacklist databases below:

• MXToolbox’s Blacklist Check
• Zerobounce Blacklist Checker
• DNSChecker IP & Email Blacklist Checker

Clean Up Your List

Once you’ve crossed domain & blacklist issues off of your checklist, take a close look at your audience list. Where are most of your subscribers signing up? When you look through your contacts, do you see suspicious emails? Keep an eye out for the following red flags:

• Contacts with gibberish first and/or last names
• Sudden influxes in subscribers from one source
• Contacts with invalid domains
• Foreign email addresses from markets you do not serve

If you see some odd-looking contacts in your list or have a large audience segment that hasn’t opened any emails in 3+ months, consider using a list cleaner. We like Zerobounce, but many list cleaners are available at various price points.

Once you sign up for a list cleaner, you can take the following steps to check your list hygiene:

1. Export contacts from your ESP
2. Import them into the cleaner 
3. Wait for processing
4. Download your contacts sorted by validity and activity

List cleaners vary, but generally, the contacts to avoid will be marked as invalid, spamtrap, or do-not-mail.

Managing and Avoiding Spam Reports

How you grow your list can matter just as much as what kind of contacts are on it. Make sure all subscribers have actively opted in for your emails. Always include an unsubscribe link in your email footer.

You never want contacts to be surprised they’re getting your emails. When contacts receive emails they did not sign up for, they’re more likely to report you as spam. Over time, spam reports can tank your email deliverability.

Additionally, avoid sending more than 3-4 emails a week and be mindful of aggressive sales tactics like all-caps, repeated exclamation points, and deceptive deals. Sometimes, even unappealing graphic design is enough to get you reported by particularly trigger-happy subscribers.

Send Frequency & Sudden Changes

Can sending too many emails get you sent to spam? Yes. How many is too many? It varies.

As frustrating as that can be, senders may find solace in the fact that deliverability changes are more often caused by a sudden change in send frequency, rather than a specific volume of emails sent. For example, if you leave your email marketing program on pause for 2 years, and then immediately start sending 3 emails a day to 5000 people, your deliverability will likely take a blow.

When it comes to send frequency, try to make gradual, strategic changes. Use segmentation & automation to send emails to the right people at the right times. Remember: When it comes to email, more is not always better!

Optimizing File Size for Email Deliverability

Emails with a very large combined file size are likely to be flagged as spam. When adding images to an email, make sure they are below 500kb each. Check out our guide to email image sizes for more info.

Here are some tools our team at Pure Firefly uses to compress and optimize images:

1. Tiny PNG
2. EZ Gif
3. Optimizilla

Senders should also be wary of large attachments. When sending a free download or .PDF, make sure the file size is below 5MB.

Other Tips and Tricks

If you’ve taken the steps above and still aren’t seeing the results you were looking for, there are a few steps you can take to make a small (but positive) impact on your sender reputation.

1. Personalize your “To” field: By including a contact’s first name, you indicate a more complete (and thus, more legitimate) record of your audience.
2. Use live text: Never send an email with only images. This can be hard for people to read and may get you caught in spam filters.
3. Reply to your emails: When contacts reply to your emails, they indicate an interest in your content. This active engagement can help you stay out of spam.
4. Add to address book: If subscribers add you to their saved contacts or address book, they are less likely to miss your emails.
5. Never embed videos: Most ESPs won’t even let you do this, because videos don’t usually render in the inbox. Resist the temptation to install any plugins that allow you to embed video – They are likely to damage your sender reputation.

BONUS: What about Machine Clicks?

Seeing contacts click every single link in your email? They may be extremely engaged, or they may be machine clicks. Some spam filters & inbox providers use automated clicks to check suspicious emails. This can even lead to accidental unsubscribes if the machine clicks on the unsubscribe link in your footer.

How do you spot machine clicks? Look for contacts that have clicked on every single link in an email in a very short time. Some ESPs (like Klaviyo) can show you on a click report if the engagement came from a bot or a human. You can also keep an eye out for trends in machine clicks coming from a particular domain.

If you do see machine clicks on several emails, it’s time for an email deliverability review. Unfortunately, there’s no way to 100% prevent automated clicks on your messages, but keeping a strong sender reputation can help limit them.

Escape Spam with Pure Firefly

Pure Firefly is a full-service email marketing agency. Our team has a combined 10+ years of experience, and we pride ourselves on providing cost-effective email solutions for small businesses, nonprofits, and schools. For help with deliverability, contact us any time!