How to check SpamAssassin score before sending

What SpamAssassin measures

SpamAssassin is an open-source spam filtering framework used by mailbox providers, hosting panels, and self-hosted mail stacks. It applies hundreds of rules to message headers and body content, assigning positive or negative points. The sum is a spam score compared to a threshold — commonly 5.0 — above which mail is more likely tagged as spam.

Rules cover obvious spam phrases, excessive capitalization, suspicious HTML structure, link density, missing text/plain parts, forged headers, and authentication hints. Negative rules reward signals like valid DKIM or mailing-list headers. The engine is heuristic, not psychic — legitimate marketing mail can trigger points if templates mimic patterns spammers abuse.

Pre-send checking approximates what downstream filters might see. It does not guarantee identical scores at Gmail or Microsoft — they use proprietary stacks — but it catches blunt mistakes early.

Why check before sending bulk campaigns

Bulk sending multiplies content mistakes. A subject line that scores badly once might still reach a colleague; the same template sent to fifty thousand subscribers generates complaints, spam folder placement, and provider throttling simultaneously.

Fixing HTML ratio, unsubscribe headers, or shouty subjects before launch protects domain reputation you spent months building. MailFleet integrates SpamAssassin inside the desktop app so checks sit beside template editing — not as an afterthought spreadsheet.

Agencies validating client creative should document pre-send scores in QA tickets. When delivery problems arise later, you have evidence the template passed review at launch time.

What to paste into a SpamAssassin checker

At minimum: subject line and body. Provide both HTML and plain-text parts if your campaign sends multipart/alternative — some rules compare ratio and missing text parts. Paste the final rendered HTML after merge tags are replaced with realistic sample values, not raw template syntax with curly braces intact unless your checker substitutes them.

Optional but valuable: From address, Reply-To, List-Unsubscribe headers, and raw header blocks when tools support them. Authentication results often live in headers added at send time — simulate expected From domains aligned with your SPF and DKIM setup.

MailFleet free checker at mailfleet.app/tools/spamassassin-checker accepts subject, HTML or plain body, optional From, and raw headers. The desktop app runs integrated scoring on the same inputs before queueing permission-based batches.

• Subject line exactly as recipients will see it
• Rendered HTML body with sample merge data
• Plain-text alternative if multipart
• From address matching production domain
• List-Unsubscribe and List-Unsubscribe-Post when applicable
• Raw headers for advanced rule triggers

Understanding score and threshold

Total score is the sum of triggered rule points. Threshold default is often 5.0 in SpamAssassin deployments. Below threshold suggests lower spam likelihood; above suggests higher. Some filters use different thresholds or combine SpamAssassin with other engines.

Aim lower than the minimum passing line — many operators target below 3.0 for marketing mail. A 4.8 that technically passes today may fail tomorrow if a provider tightens rules or your volume spikes.

Do not chase zero at all costs. Minor positive hits on legitimate newsletters are normal. Focus on high-weight rules: pharmaceuticals spam patterns, excessive links, ALL CAPS subjects, HTML-only with tiny text, or missing unsubscribe signals.

Reading triggered rules table

Each triggered rule shows a name, point value, and short description. Sort mentally by points — fixing a 2.5 rule matters more than a 0.1 rule. Rule names like HTML_IMAGE_ONLY_24, SUBJ_ALL_CAPS, or URIBL_BLACKLIST point to specific remediation.

Some rules reference external blocklists for linked domains. A compromised tracking domain in your template can spike scores until URLs are replaced. Others flag formatting — font color mimicking hidden text, excessive exclamation marks, or deceptive subject/body mismatch.

MailFleet checker displays triggered rules with recommendations. Re-run after each fix to confirm points dropped. Screenshot results for client approvals when needed.

Subject line risk patterns

Subjects drive first impressions and trigger dedicated rules. ALL CAPS, excessive punctuation!!!, fake RE: or FWD: prefixes, and spammy financial promises add points fast. Emoji-heavy subjects can trigger in some configurations.

Honest, specific subjects outperform clickbait for both SpamAssassin and human readers. Product name plus concrete benefit beats vague urgency. Test two subject variants through the checker before A/B splits in production.

Keep length reasonable. Extremely short or empty subjects look suspicious. Extremely long subjects may truncate awkwardly on mobile clients — a UX issue adjacent to filtering.

HTML and plain-text body issues

HTML-only messages with little extractable text score poorly — always include a meaningful plain-text part. Image-heavy templates with minimal text resemble classic spam layouts. Balance images with readable copy.

Link density matters: too many URLs relative to text triggers rules. Consolidate calls to action. Ensure link domains are reputable and not on blocklists. Shorteners sometimes add risk unless widely trusted.

Inline CSS and table layouts are normal for email; broken HTML nesting can confuse parsers into higher scores. Validate rendering in real clients after SpamAssassin passes.

Headers that affect SpamAssassin

List-Unsubscribe and List-Unsubscribe-Post headers signal legitimate bulk mail to filters and regulators. Missing unsubscribe mechanisms hurt both CAN-SPAM compliance and heuristic scores for marketing messages.

From and Reply-To should align with authenticated domains. Mismatched or default noreply patterns can add suspicion when combined with promotional content. Message-ID and Date headers should look well-formed — broken headers trigger MIME rules.

Paste simulated headers into advanced checkers when validating templates before MailFleet sends through your SMTP or API provider. After live test sends, use mailfleet.app/tools/email-header-analyzer on received messages to compare.

Authentication interaction with content scores

Valid DKIM can apply negative points — good — while missing SPF/DKIM hints add positive points on some rulesets. Content checks do not replace DNS authentication. Run SPF, DKIM, and DMARC tools on mailfleet.app alongside SpamAssassin.

A low SpamAssassin score with broken authentication still filters badly. A moderate score with strong authentication and engaged permission-based lists may perform fine. Treat both layers in pre-send checklists documented at mailfleet.app/resources/email-deliverability-checklist.

Provider-added headers at send time affect final received scores. Pilot sends through MailFleet to seed inboxes reveal real-world header context beyond static paste checks.

Workflow inside MailFleet desktop

Build or import templates in MailFleet on Windows, macOS, or Linux. Before queueing a campaign, run integrated SpamAssassin analysis from the template workflow. Review score, triggered rules, and capacity scoring together — content and volume interact with reputation.

Fix issues in the template editor, re-run until comfortable, then send a pilot batch to a small permission-based segment. Read campaign logs for deferrals unrelated to SpamAssassin — provider limits still apply.

License pricing: pay.mailfleet.app/buy/1year ($49) or pay.mailfleet.app/buy/lifetime ($79). Linux installs use DEB or RPM on x86_64 or ARM64 — no AppImage. Download from mailfleet.app/download.

Using the free web SpamAssassin checker

Teammates without MailFleet installed — copywriters, clients, contractors — can use mailfleet.app/tools/spamassassin-checker. Paste subject and body, complete captcha, review results. Share links or screenshots in review threads.

Public checker includes rate limits and captcha to prevent abuse. For high-volume QA, prefer desktop integrated checks or local spamc if your infrastructure team runs SpamAssassin on servers.

Docs at mailfleet.app/docs/spamassassin-checks explain rule categories and MailFleet-specific integration points.

Common false positives and how to handle them

Legitimate finance, medical, or compliance terms may trigger keyword rules in sensitive industries. Rewrite for clarity without sensationalism. Add plain-text balance and reduce link counts rather than stripping required legal language entirely.

Personalization placeholders sometimes confuse checkers if left as bare merge tags — use realistic sample values during QA. Tracking pixels and open-tracking links add URLs; minimize redundant trackers.

If score stays borderline after reasonable edits, pilot send to seeds and monitor placement. SpamAssassin is one signal — engagement metrics from permission-based audiences matter too.

Iterative fix and re-test loop

Establish a team rule: no full-list send without documented SpamAssassin pass below your internal threshold. When rules trigger, assign owners — copy, design, or ops — based on rule category.

Version templates in Git or DAM with score snapshots in commit messages or tickets. Regression happens when someone swaps an image URL to a blocklisted domain three months later.

After major provider or domain changes, re-run checks even if templates unchanged — authentication headers in pilot sends may differ.

SpamAssassin limits and complementary checks

SpamAssassin does not measure list quality, consent, or inbox placement at Gmail. It does not replace seed testing, Google Postmaster Tools, or Microsoft SNDS for domain reputation monitoring.

Combine with bounce suppression, complaint handling, and responsible sending policy on permission-based lists only. MailFleet is not a spam tool — unsolicited mail violates Acceptable Use Policy regardless of score.

Use SMTP diagnostics and bounce code lookup tools when logs show failures unrelated to content scoring. Multi-signal debugging beats chasing a single number.

Building a team QA rubric around SpamAssassin

Define an internal threshold stricter than the default 5.0 — many MailFleet operators use 3.0 for marketing mail. Require screenshot or exported rule tables in creative approval tickets. Assign copywriters responsibility for subject rules, designers for image-to-text ratio, and ops for header completeness.

Regression tests matter: when a template ships monthly, re-run checks anyway. Third-party tracking domains get blocklisted without notice. A template that scored 1.2 in January may score 4.6 in June because a footer link rotted.

Pair rubric items with responsible sending policy training so new hires understand that low scores do not authorize mailing purchased lists. Permission and content quality are independent gates.

Agency workflows for client template approval

Agencies should run client creative through mailfleet.app/tools/spamassassin-checker before internal stakeholder review — clients without MailFleet installs still participate. Attach triggered rules to PDF approvals so scope arguments later have paper trail.

When clients insist on risky copy — excessive urgency, misleading subjects — document that SpamAssassin flagged specific rules and that delivery risk rises. Professional agencies protect themselves with QA records, not verbal disclaimers.

After approval, send MailFleet pilot batches from the client provider profile and compare received headers to pre-send checker inputs. Differences between paste checks and live sends teach which headers your provider adds automatically.

Scoring HTML newsletters vs plain operational updates

Marketing newsletters with rich HTML, multiple CTAs, and tracking pixels naturally score higher than plain operational notices. Set different internal thresholds per template class — a changelog email should be stricter than a monthly promo. Document thresholds in your QA wiki so reviewers apply consistent standards.

Operational mail still needs plain-text parts and honest subjects. A billing alert with spammy urgency language triggers the same rules as marketing hype. Run checks on every template type before MailFleet queues permission-based batches.

When migrating templates from a cloud ESP, paste the exported HTML into the checker before assuming parity. ESPs sometimes inject footer compliance blocks that help scores — verify those blocks exist in your MailFleet templates too.

Automating checks in CI for template repositories

Teams storing email HTML in Git can curl the MailFleet web checker API where permitted or run local spamc in CI pipelines for pull request gates. Fail builds when scores exceed threshold on changed templates — same philosophy as unit tests for application code.

CI automation does not replace human review for tone or legal copy, but it prevents obviously broken templates from merging. Pair automated scores with required reviewer sign-off for client-facing campaigns.

Document CI thresholds separately from production marketing thresholds if transactional templates naturally differ. One global number causes false failures or false confidence.

Store historical checker outputs with campaign IDs so postmortems after deliverability incidents can distinguish template regressions from list or authentication problems that occurred the same week.

• Gate template PRs on score regression
• Keep human review for legal and brand tone
• Re-run checks after provider or domain changes

Post-send correlation when scores looked fine

If recipients still report spam folder placement despite low SpamAssassin scores, investigate authentication alignment, list engagement, and complaint rates before rewriting copy again. Content score was only one gate.

Pull received headers from affected recipients using mailfleet.app/tools/email-header-analyzer. Compare Authentication-Results to what you simulated in the checker. Provider-added signatures and list-unsubscribe headers may differ from paste tests.

MailFleet campaign logs show whether messages were accepted, deferred, or rejected at SMTP layer — distinct from spam folder placement downstream. Multi-layer debugging separates content issues from reputation issues from authentication issues.

Schedule quarterly template re-checks even when creative is unchanged — external blocklists and link rot are time-dependent risks that static archives will not catch.

Share checker results with stakeholders who do not use MailFleet desktop so marketing, legal, and client approvers work from the same objective score snapshot before any production send.