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§ T-03  —  Tool← All tools

Email spam
checker

Test your subject line and email content for spam trigger words, punctuation issues, and other factors that cause emails to land in spam folders.

Analyze email content
§ 01Spam factors

Why emails go to spam.

Spam filters look at dozens of signals. Content is just one part of the picture.

Spam trigger words

Words like "free", "guaranteed", "click here", and "act now" score heavily with spam filters. Even one or two can tip the scales.

Missing authentication

Without SPF, DKIM, and DMARC configured, receiving servers cannot verify your email is legitimate. Authentication failures are the leading cause of spam classification.

Poor sender reputation

Email providers track bounce rates, spam complaints, and engagement over time. A low sender reputation score means even clean emails land in spam.

Excessive capitalization

ALL CAPS SUBJECT LINES and words in all caps look like shouting and are heavily penalized by spam filters. Use sentence case.

High bounce & complaint rates

If many recipients report your emails as spam or addresses bounce, providers penalize future emails from your domain.

Purchased email lists

Bought lists have unverified addresses, old data, and spam traps. Sending to them destroys your sender reputation quickly.

Send emails that reach the inbox.

Plunk automatically handles SPF, DKIM, and DMARC authentication — the most critical deliverability factor. Start free, no credit card required.

Start with PlunkDeliverability guide

Frequently asked questions

What is a spam checker?

A spam checker analyzes email subject lines and content for characteristics that spam filters use to block or flag emails. It looks for spam trigger words, excessive capitalization, suspicious punctuation, and other signals that inbox providers associate with spam. Running your email through a spam checker before sending helps improve deliverability.

What causes emails to go to spam?

Emails land in spam for many reasons: spam trigger words in the subject or body, poor sender reputation, missing SPF/DKIM/DMARC authentication, sending to purchased or unengaged lists with high bounce rates, excessive links or images, HTML-to-text ratio issues, or being reported as spam by previous recipients. Authentication issues and sender reputation are the most common causes.

How do I check if my email will be spam?

Use a spam checker tool like this one to analyze your subject line and content. Also check your email authentication setup—verify that SPF, DKIM, and DMARC are correctly configured for your domain. Send test emails to spam testing services, and monitor your deliverability metrics (bounce rate, spam complaint rate) over time.

What are spam trigger words?

Spam trigger words are phrases commonly associated with spam emails. They include words like "free", "guaranteed", "act now", "click here", "make money", "winner", "prize", "urgent", and many others. Spam filters assign point values to these words, and emails exceeding a threshold score are flagged or blocked. Avoiding these words and using natural language improves deliverability.

Is email authentication important for avoiding spam?

Yes—email authentication (SPF, DKIM, DMARC) is critical. Without proper authentication, receiving mail servers have no way to verify your email is legitimate, making it more likely to be treated as spam. Since 2024, Gmail and Yahoo require DMARC authentication for bulk senders. Properly authenticated emails with a clean sender reputation reach the inbox far more reliably than unauthenticated emails.