Migomail's spam testing engine checks every email against 30+ spam filter rules, runs inbox placement tests across 8 major mail providers, evaluates your authentication headers, and flags HTML and content issues — before your campaign reaches a single real subscriber.
Spam filtering is not one check — it is content scoring, authentication verification, HTML validation, link scanning, and inbox placement prediction running in parallel. Migomail runs all of them in under 60 seconds.
Run your email through SpamAssassin — the most widely deployed open-source spam filter used by Gmail, Yahoo, and ISPs worldwide — and see a score from 0 to 10+. Below 3.0 passes most filters; above 5.0 will be flagged or rejected by corporate spam gateways. Every rule that fired is shown with its individual score contribution.
Send to seed addresses at Gmail, Outlook, Yahoo, Apple Mail, Hotmail, AOL, Protonmail, and GMX — and see exactly where your email lands: Primary Inbox, Promotions, Spam, or Not Delivered. Results return within 60 seconds per provider.
DKIM signature validation, SPF record check for the sending IP, DMARC policy evaluation, and From domain alignment check — before the content is even evaluated. Any authentication failure that would cause a filter to reject your email is flagged with the exact DNS record that needs fixing.
Check 50+ HTML rules: missing alt text, excessive inline CSS, image-only emails, unsupported CSS properties, broken table structures, and any JavaScript that triggers spam filters. The report maps each identified issue to the specific clients it affects.
Every link in your email is checked against Spamhaus DBL, SURBL, and URIBL — including redirect chains and tracking domains. A single blacklisted URL in one link triggers spam filters for the entire email, even if the link belongs to a third-party analytics domain.
Check for all-caps subject lines, excessive exclamation marks, 200+ trigger phrases like "FREE" or "CLICK HERE", base64-encoded invisible text, misleading sender information, and every content pattern documented across major spam filter rulesets.
Paired with spam testing: see how your email renders in Gmail, Outlook 2019/2021/365, Apple Mail, iOS Mail, and Android Gmail. Rendering issues that also trigger spam filters — like broken layouts from unsupported CSS — are cross-referenced in a single report.
After reviewing your spam test report and making changes, re-run the test with a single click on the same template and subject line — and see the score change immediately. Test history per campaign shows the progression from initial score to final pre-send score.
A score of 3.2 tells you there is a problem. The Migomail breakdown shows you exactly what is contributing each point — and which two changes will bring the score below 2.0 fastest.
Score of 3.2 — some filters may flag this email. Fix the 2 flagged items to bring the score below 2.0 for safe delivery everywhere.
Placement tests send to real seed mailboxes and report actual folder placement — not estimates. Results shown here are for the fixed version (score 1.4) of the same email shown in the score breakdown above.
AOL routing to Promotions is a sender-reputation threshold issue, not content-related — see remediation guidance in the full report.
Most marketers know to avoid "FREE MONEY!!!" — but the most common spam filter triggers are far more subtle. Migomail checks for all of them. These are the ones that appear most frequently in our testing data.
Spam testing is built directly into the Migomail campaign builder — no third-party tools, no CSV exports, no separate testing platforms needed.
The spam report tells you what to fix — not just what is wrong. These are the six most frequently flagged issues in Migomail spam tests and the changes that resolve them.
Feedback from email managers and deliverability leads who use Migomail spam testing as part of their mandatory pre-send checklist.
We had a campaign where Gmail inbox placement dropped from 96% to 41% overnight with no apparent reason. After running the Migomail spam test, we found the issue in 3 minutes: a third-party analytics script a developer had added to the email template the previous week was triggering SpamAssassin's JavaScript detection with a score contribution of +4.8. One script tag was routing 55% of our Gmail sends to spam. We removed it, re-tested (score dropped to 0.9), and inbox placement recovered to 94.6% by the next campaign. Without the per-rule breakdown showing "JavaScript detected — +4.8," we would have been troubleshooting for weeks.
The inbox placement test across 8 providers is the feature I use most. Our subscriber base is international — roughly equal splits across Gmail, Outlook, and Yahoo. A campaign that passes Gmail inbox placement but lands in Yahoo spam is still a 30% revenue miss. Before Migomail, we only tested Gmail. The first time I ran the full 8-provider test, I discovered that 3 of our last 8 campaigns had landed in Yahoo spam — campaigns we considered successful based on our Gmail-dominant open rate data. The Yahoo routing issue was a tracking domain that had appeared on URIBL. We would never have caught it with a single-provider test. After fixing the tracking domain, our overall open rate increased by 12 percentage points overnight. That is what testing across all providers instead of one does for you.
Our agency runs 40–60 campaigns per month across a dozen clients. Before Migomail spam testing, we relied on individual judgement about what content would trigger filters — and we were wrong often enough to cause real client problems. Now we run a spam test on every campaign. Last month it flagged that a client's email had a link redirecting through a shortened URL to a domain that had been on the Barracuda blacklist for 3 weeks. The client's brand domain was clean — the blacklisted domain was a redirect hop on a third-party affiliate link. Without the link chain scan Migomail runs, we never would have found it before sending to 80,000 subscribers.
“Rackwave Technologies has significantly improved our marketing performance while providing reliable cloud services. We’ve been using their solutions for a while now, and the experience has been seamless, scalable, and results-driven.”
David Larry
Founder & CEO
Common questions about email spam testing and deliverability pre-checks.
A spam score is a numeric rating from SpamAssassin that represents how "spammy" an email looks based on content, structure, authentication, and links. Scores range from 0 (clean) to 10+ (near-certain spam). Most ISPs and corporate gateways reject emails above 5.0. Gmail and Yahoo use proprietary algorithms, but SpamAssassin scoring is a strong proxy. Aim for a score below 2.0 for safe delivery across all major providers. Above 3.0 indicates specific issues that should be fixed before sending.
A spam score tells you what content rules your email triggers. An inbox placement test tells you where your email actually lands. Migomail sends to real seed addresses at Gmail, Outlook, Yahoo, Apple Mail, and other providers and reports back which folder the email appeared in: Primary Inbox, Promotions Tab, Spam, or Not Delivered. A spam score is an estimate; a placement test is a measurement. Both together give the complete picture — the score tells you why, the placement test confirms the outcome.
Different mailbox providers use different spam filtering algorithms and blacklists. An email that passes Gmail's filters may still trigger Yahoo's or Outlook's. Gmail, Yahoo, and Outlook together account for approximately 90% of global email usage, but their filtering behaviour differs significantly. A single-provider test gives you an incomplete picture — Migomail tests across 8 providers simultaneously.
No — spam testing identifies authentication problems, but the fix is implementing proper authentication, not adjusting the test. Authentication failures are among the highest-scoring spam filter triggers and cannot be addressed through content changes. DKIM, SPF, and DMARC setup is a prerequisite for passing spam tests and must be done at the DNS level.
Before every campaign send. Even established templates can be affected by: a tracking domain appearing on a blacklist, a new link added with a spam phrase, changes to DNS configuration, or content edits introducing trigger phrases. The test takes under 60 seconds, so running it as the final step before every campaign adds minimal time and eliminates a significant category of preventable deliverability failures.
Migomail checks 50+ HTML rules including: missing DOCTYPE, malformed table structures, JavaScript in the email body, external CSS stylesheet links, form elements, missing alt text on images, images larger than recommended limits, broken MIME structure, and non-standard font sizes. Each issue is flagged with the specific element and tag location.
No — a low spam score is necessary but not sufficient. Spam filters have two layers: rule-based content scoring (what SpamAssassin measures) and reputation-based filtering (what Gmail, Outlook, and Yahoo apply based on sending IP, domain history, and engagement). Spam testing addresses the content layer — the reputation layer requires warmup, bounce management, and list hygiene practices.
Yes. Migomail maintains a spam test history per campaign — every test run is timestamped and stored with the full score breakdown, placement results, and authentication status. You can compare results before and after a content change to measure the score improvement. Test history is retained for the life of your account and is exportable. You can also share a read-only test report link with team members or clients.