Key takeaways ✨
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If you’re like the 55% of marketers who use promotional or marketing emails, you know that they have a huge impact on lifecycle marketing. But did you know over 14% of all emails never make it into the inbox?
While email deliverability can feel like a bit of a mystery at times, you don’t have to cross your fingers and hope that your messages end up where you intend. With Litmus Spam Testing, you can identify and fix issues that might otherwise land your emails in spam—long before you hit send.
Read on to learn what impacts email deliverability and why running regular spam tests is important for maintaining and improving your inbox placement.
Table of contents
- What factors affect email deliverability?
- Why is email spam testing important?
- What is Litmus Spam testing?
- How to get started with Litmus Spam Testing
- How do you read the spam test results
- Why you need to run spam tests regularly
What factors affect email deliverability?
A lot of factors affect your email deliverability including email authentication, sender reputation, and the actual content of your email, to name a few.
Litmus’ Pre-Send Spam Test helps you spot issues that could land your email in spam, so you can fix them before pressing send. Here are the main filters it tests against and why they matter.
Email authentication
Email authentication looks at the source of an email to see if it’s valid. Also called domain authentication or validation, email authentication helps prevent spoofing and phishing scams from phony email addresses (like emails pretending to be from your boss or your bank—but aren’t).
Here are some of the authentications our email spam test considers:
- DomainKeys Identified Mail (DKIM). Shows that your email is associated with your domain. In turn, it essentially allows your organization to claim responsibility for your email.
- Domain-based Message Authentication, Reporting & Conformance (DMARC). Meant to combat phishing and helps you identify if a sender is attempting to impersonate you.
- List-Unsubscribe. An optional email header that allows for an easy and consistent unsubscribe action.
- Sender Policy Framework (SPF). Allows a domain owner to indicate multiple IP addresses or domains that can send mail on their behalf via a DNS TXT entry.
- TLS, STARTTLS, or Opportunistic TLS. Gives senders the ability to encrypt email in transit.
- Brand Indicators for Message Identification (BIMI). A way for inbox providers to verify information about your brand. Allows you to display a sender logo alongside your messages in the inbox for better trust and visibility.
Placement filters
Placement filters evaluate emails against a set of criteria—which changes over time. These filters look at a combination of engagement, reputation, authentication, formatting, and content. (But not necessarily spam word triggers in the subject lines and copy—those are a thing of the past.)
Litmus Spam Testing checks your email against the following placement filters:
- AOL Mail
- Gmail
- GMX
- GoDaddy
- G Suite
- Mail.com
- Mail.ru
- Office 365
- Outlook
- Web.de
- Yahoo
Score filters
These scores show you the likelihood a spam filter tool will catch your email and put it in someone’s spam inbox.
- Barracuda. Barracuda Essentials for Email Security is a sophisticated anti-spam and email analysis tool often used by large organizations.
- Microsoft Exchange Online Protection. Uses a built-in malware and spam filter to evaluate and score email.
- Outlook Desktop. Outlook comes with a built-in junk email filter that “learns” spam emails over time.
- SpamAssassin. An open source spam filter that analyzes email headers and body text by using text analysis, bayesian filtering, DNS blocklists, and collaborative filtering databases.
Blocklist filters
A blocklist is a real-time collection of senders thought to be sources of spam or other types of email abuse. Blocklist providers may use a combination of spam traps, spam complaints, and other proprietary data sources as criteria for adding a sender to a blocklist. Inbox providers often maintain their own proprietary blocklists, using them in combination with independent, third-party blocklists.
Land in inboxes, not spam folders Scan emails across 20+ spam filters, improve deliverability, and integrate seamlessly with your ESP. 
Why is email spam testing important?
You can’t simply look at an email and know if it will land in a spam folder.
Avoiding the spam folder is more complex than it used to be. Many issues could potentially land you in the spam folder that you can’t predict manually—from blocklists to email content to varying scores and weights that a spam filter uses to decide whether an email is spam.
In early 2024, Google refined their sender requirements and guidelines to help ensure messages are delivered to Gmail accounts as expected. Its goal was to “…prevent Gmail from limiting sending rates, blocking messages, or marking messages as spam.” They also outlined clear guidelines to help users prevent their emails from going to spam.
Emails in the spam folder waste your opportunity
Nearly 65% of email marketers who responded to our 2023 State of Email Report ranked email among their top three most important marketing channels. If your emails are landing in the spam folder, you’ve missed out on all that opportunity!
Protect your email deliverability and sender reputation
Spam testing can help you spot—and correct—issues before you send. If you never send errors, your email deliverability and sender reputation should get a boost.
Send emails your subscribers are excited to open and click
You’re sending emails to engage subscribers with some goal in mind. But the ways in which they engage with your messages also shows inbox providers people actually want to engage with your messages. When they know you’re a trusted sender, inbox providers are more likely to put your messages where you want them—the inbox!
Why you need to run spam tests regularly
Email clients update every 1.2 days on average, and you may be completely unaware of the changes. In the same way, the algorithms for spam filters update regularly. And sometimes, your IT or dev team may change an IP address without realizing it impacts email. At any rate—an email spam test helps keep you in the know!
“We run an abbreviated spam test every time an email is sent in for QA. More often than not, it’s all we need and is built directly into our workflow. If there’s an unexpected flag, then we’ll run a complete check to see what’s going on.”
Landing in the spam folder is more than just bad for your marketing campaigns and reputation. It costs you in the form of wasted resources, lost revenue and missed opportunities to connect with your subscribers. In some cases, it may even require hiring a company to fix your sender reputation.
What is Litmus Spam Testing?
Litmus’ Spam Test tool scans your emails against 20+ different tests, identifying any potential issues that could prevent you from landing in the inbox. Best of all, it provides actionable advice on how you can fix them, before you hit send.
“What you do before you press send will determine whether your email reaches the inbox or the spam folder. Litmus Spam Testing helps marketers catch potential issues before they impact campaigns, protecting sender reputation and ensuring emails land where they belong: front and center in the subscribers’ inboxes.”
How to get started with Litmus Spam Testing
All Litmus Plus and Enterprise plans include spam testing. There are three different ways to run a spam test in Litmus: manually, via esp sync, and automatically.
Run a manual spam test in Litmus
Here are the steps to run a complete check against all filters:
- Log in and navigate to the “Test” tab.
- Select “View and create spam tests” in the slider menu.
- Start a new spam test or see the results of a recent one.
Run a spam test using ESP Sync
You can also use ESP sync to speed up the process by choosing an email that’s already in your drafts. Litmus will pull this email in when you start a new spam test.
Run an abbreviated spam test
Finally, you can run an abbreviated spam test each time you send in a test email to Litmus.
Simply send your email to Litmus using your Litmus test address. Then navigate to the bottom of your Previews & QA results. This will show you your DKIM, DMARC, SPF and BIMI authentication results, as well as the Outlook Desktop filtering and domain blocklist results.
The most critical errors will usually show up in your authentication. This abbreviated test highlights key results and is the perfect solution for most busy marketing teams.
Maximize your email reach Check against 20+ spam filters. Verify authentication. Get advice to improve deliverability.
How do you read the Litmus Spam Test results?
Once your spam test has run, you’ll see a high-level summary of your results. From here, you can drill deeper into issues that were uncovered.
“Our test does not have the benefit of knowing your inbox behavior, so it’s behaving more like someone you have never emailed before. (So basically, it’s the out of the box settings—not influenced by knowing any behavior). Therefore, it’s showing you where Gmail will put your email if Gmail has no additional knowledge.”
Green square = passed
If a filter shows a green square or says “Passed”, you’re good to go!
Yellow square = minor issue
If a filter shows a yellow square or is marked as a minor issue, you can still move forward with your send. However, it’s a good idea to review what the filter flagged so you can monitor the issue. Unaddressed issues can become critical over time.
Red square = critical issue
If a filter shows a red square or is marked as a critical issue, do not hit send until you resolve the issues flagged. When you click to review the results of that filter, you’ll see a sidebar with recommended action steps. You may want to involve the person that manages your email infrastructure to help you figure out issues to resolve before you continue sending emails.
If a filter is unavailable, that means that we didn’t receive your test. There could be several reasons for this that we can help troubleshoot.
Catch errors early so every email lands in the inbox
Make it a best practice as part of your email workflows to run spam tests regularly, and keep your email campaigns alive and well. Try Litmus Spam Testing and other helpful Litmus features for free.
Try Spam Testing free for 7 days
Sign up for a trial of Litmus Plus to try Spam Testing, Email Previews, and more free for 7 days.
Lindsey is a Sr. Content Marketing Manager at Litmus.
