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Email Spam Tester vs GMass
GMass is a Gmail mail-merge extension with a free tester that shows which Gmail folder your email reached. This page compares that tester with ours, not the mail merge.
Pick Email Spam Tester if
- your list is not only Gmail: you need Outlook, Yahoo and other providers too
- you want to know why a message went to spam, not only that it did
- you want the score, the authentication results and the folder in one report
- you want to test from a script, with a free API
Pick GMass if
- you send cold email from Gmail and already use GMass, whose paid Spam Solver runs the test from inside the compose window
- Gmail and Google Workspace are the only inboxes your recipients use
Run both tests on the same email
The fairest comparison is your own message. Get an address, send the email you were going to test anyway, and put the two reports next to each other.
Side by side
| Feature | Email Spam Tester | GMass |
|---|---|---|
| What it is | A spam and inbox test | A Gmail mail-merge extension with a free Gmail folder tester |
| Providers in the placement test | Gmail, Outlook, Yahoo and other providers | Gmail and Google Workspace |
| Spam score | 0 to 10 and 0 to 100 | None in the tester |
| SPF, DKIM, DMARC, blocklists | In the same report | In a separate analyzer, without a score |
| Content, links, HTML | Yes | Not in the tester; a separate Link Checker and Email Analyzer |
| Bulk-sender rules and one-click unsubscribe | Checked | Its tester advises removing the unsubscribe link for the test |
| Fix plan | Ordered fixes with DNS records | A general fix list on the page |
| API for testing | Free | No tester API; the GMass API needs the Premium plan |
| Price | Free | Tester free; GMass from $29.95/month in USD (January 2026 price list; the pricing page adjusts by country) |
| Languages | 31 | English |
Gmail is not the whole list
The GMass tester lists its seed addresses, and every one of them is a Gmail or Google Workspace mailbox; its own FAQ calls it a check of the Gmail folder. If your recipients are mostly on Gmail, that is a useful free signal.
Most lists are mixed. Outlook.com has required authentication from bulk senders since May 2025, Yahoo has its own rules, and a message can sail into Gmail's Primary tab while Outlook files it as junk. The placement option here shows Gmail, Outlook, Yahoo and other providers side by side from one send.
Why it landed there
The GMass tester tells you where the email went. Why it went there is a job for its separate Email Analyzer, which reads SPF, DKIM, DMARC and blacklists but gives no score, and for your own reading of the content.
Email Spam Tester puts the folder and the reasons in one report: 42 checks across authentication, infrastructure, spam engines, content and the bulk-sender rules, plus recommendations that never cost points, two scores, and a short list of fixes in the order that matters, with the DNS records written out.
About removing the unsubscribe link
Among its tips, the GMass tester suggests removing the unsubscribe link and turning off tracking for the test. It also means you test a message you will not send. Gmail and Yahoo require bulk senders to include a working one-click unsubscribe, so a campaign without one is not the campaign that goes out. Here, the test is meant for the exact email you will send, unsubscribe header included, and the report checks that header too.
What people who tried it said
I took a closer look at it, and it convinced me. […] Every warning names the RFC section behind it. You don't have to believe the tool, you can check it.
Translated from GermanIch habe ihn mir genauer angesehen, und er hat mich überzeugt. […] Jede Warnung nennt die zugrunde liegende RFC-Stelle. Man muss dem Tool nicht glauben, man kann es nachprüfen.
Philipp ZöldEmail deliverability consultantlinkedin.com If you send emails and you don't know where they land, it's a simple first check. And it costs nothing.
Vincent RobinCo-founder, My Deliverability Expertlinkedin.com I just tried your tool and I really like it - good job!
Georg LauterbachMaintainer, docker-mailservergithub.com Questions
Is the GMass inbox tester free?
Yes. You send your campaign to the addresses on its page and watch which Gmail folder each one reaches. GMass itself, the mail-merge extension, is paid after a seven-day trial.
Does GMass test Outlook and Yahoo?
Its inbox tester lists Gmail and Google Workspace addresses only. Email Spam Tester's placement option covers Gmail, Outlook, Yahoo and other providers.
Do I need a Gmail account to use Email Spam Tester?
No. You send from wherever you normally send: your mail client, a sending platform, your own server. There is no account of any kind.
Can I use both?
Yes. For a list that is mostly Gmail, the GMass tester is a quick look at Gmail folders; for the reasons behind a result and for the other providers, use the full report here.
Other comparisons
All comparisonsRun both tests on the same email
The fairest comparison is your own message. Get an address, send the email you were going to test anyway, and put the two reports next to each other.