If your email lands in spam, the first step is knowing why. The tools below each check a different slice of the problem. This guide compares what each one actually tests, what it costs, and which fits cold email, transactional email, and agencies.
Most senders need two layers: a free DNS/authentication check (SPF, DKIM, DMARC, TLS, IP reputation) to catch the common failures, and inbox-placement testing when you need proof of where a real message lands. The free layer is where most problems are found.
| Tool | What it checks | Inbox placement | Price |
|---|---|---|---|
| Inboxproof | MX, SPF, DKIM, DMARC, TLS, PTR, IP reputation (RBL), spam-risk score | No | Free; Pro adds monitoring + API |
| Mail-Tester | Sends a test email; 0-10 spam score, SPF/DKIM/DMARC | No | Free |
| GlockApps | Inbox placement across Gmail/Outlook/Yahoo + deliverability | Yes | Paid (trial) |
| InboxMonster | Inbox placement + deliverability monitoring | Yes | Paid |
| 250ok | Deliverability + inbox placement + monitoring | Yes | Paid |
| Litmus | Design, cross-client rendering, analytics | No | Paid (enterprise) |
| MXToolbox | DNS/MX/SPF/DMARC lookups, blacklists | No | Free |
| Sender Score | IP/domain reputation score (0-100) | No | Free |
Inboxproof runs the full free authentication stack in one pass: MX, SPF, DKIM, DMARC, TLS, PTR and IP reputation (RBL), plus a single 0-100 spam-risk score with the exact fix for anything failing. No signup. Best when you want a fast, complete domain check before you send. Try the spam checker or the DMARC checker.
Mail-Tester sends a real test email and returns a 0-10 spam score. Good for a second opinion on a specific message, but it tests one email at a time and the score is less granular than a full DNS + reputation pass.
GlockApps, InboxMonster and 250ok do what the free tools can't: they send test campaigns and show you whether a real message lands in the inbox, spam or promotions. Worth the cost when you're scaling volume and need placement proof. None of them replace the free authentication checks, which catch the majority of problems first.
Litmus is for design and rendering, not deliverability. Use it if your problem is how email looks, not whether it arrives.
MXToolbox and Sender Score are excellent free single-purpose checks (DNS records and IP reputation respectively). Inboxproof bundles those same signals into one report so you don't have to bounce between sites.
Related: Mail-Tester alternatives · GlockApps alternatives · free spam checker · all guides
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