Inbox placement test
An inbox placement test sends a message to a curated set of seed addresses across every major mailbox provider and reports back where each copy landed — inbox, promotions, spam, or missing entirely.
- Seedlist test, deliverability test
- Folder placement per provider, not delivery rate
- Gmail, Outlook/Microsoft 365, Yahoo, Apple, corporate filters
- Before every campaign launch and weekly during sends
What it is
Most senders look at delivery rate — accepted-by-the-receiver divided by attempted. That number is almost useless because it tells you nothing about folder placement. A message can be accepted with a clean 250 OK and dropped straight into the spam folder. Inbox placement tests close that gap by actually probing where mail lands.
The mechanism is simple. The test provider maintains live mailboxes — a "seedlist" — at every major free mailbox provider and at a sample of corporate filters. You add the seedlist addresses to your campaign or send a test directly. After a few minutes the provider scans each seedbox, sees which folder the message landed in, and aggregates the result into a placement breakdown.
What it reports
A typical report shows, per provider: percentage in primary inbox, percentage in promotions or other tabs, percentage in spam or junk, and percentage missing entirely (which usually means a 5xx rejection at the SMTP layer or an aggressive content filter). Good tools also show authentication results — SPF, DKIM, DMARC pass/fail — and whether your IPs or domains are on any of the major blocklists at the moment the test ran.
Treat the percentages as directional, not exact. Seedboxes don't have the engagement history of a real recipient, so they tend to underestimate inbox placement at Gmail and overestimate it at Outlook. But the trend lines are reliable — a placement test that shows you going from 80 percent inbox to 40 percent inbox is real, even if the absolute numbers are off by a few points.
How NeverSpam does it
NeverSpam runs continuous placement testing as part of warmup itself. Every warmup conversation between your sender and our network is a miniature placement test: we know exactly which folder it landed in because the receiving address belongs to our network. That data feeds a live dashboard showing folder placement per provider and per campaign — separately for the warming template versus the live campaigns you're running.
That continuity is unusual. Standalone test tools — GlockApps, Inboxally, Mailgenius, Validity Everest — run on demand against fresh seed addresses. The result is a snapshot. Continuous testing lets us catch placement drift the day it happens rather than the week after.
Why it matters
Cold-email senders typically discover deliverability problems through reply-rate declines, which lag the underlying placement issue by days or weeks. By the time you notice, your sender has already taught Gmail that mail from your template belongs in spam — and reversing that learning takes longer than building it did.
Run inbox placement tests before every new template goes live. Run them weekly while you're sending. Compare placement across templates when reply rates diverge — content fingerprinting is real and measurable.
Related
- Email deliverability — what placement is actually measuring
- Sender reputation — the upstream driver of placement
- Template-based warmup — placement improvement, productised
- Cold email deliverability checklist
- NeverSpam's continuous placement dashboard