Inbox Intelligence (inbox placement)

What this tells you

Blacklists and deliverability show whether your DNS and SMTP are healthy. Inbox Intelligence shows what Gmail actually does with a message from your domain: the placement your recipients experience. Results reflect your live sending reputation, authentication, and content signals.

How a placement test works

1. Open Inbox Intelligence in the sidebar and click New Test.
2. Enter your From email: the exact address you will send from (must match the message you send).
3. Click Start test. SenderSignal assigns:
   • A unique Placement ID (embedded in your email so we can find it in seed mailboxes)
   • A list of seed addresses across Gmail / Google Workspace mailboxes we monitor
4. Compose and send one email from your SMTP or ESP, not from SenderSignal. Include the Placement ID in the body (HTML or plain text). Send to all seed addresses (copy the list or download CSV).
5. SenderSignal polls seed mailboxes automatically. Results update on the test page as each seed is found: inbox folder, spam, promotions, etc.

Send from your SMTP (important)

The test must originate from your mail server or sending platform, using the From address you specified. That is what makes results meaningful: they reflect your domain's authentication path, IP reputation, and content scoring, not a third-party relay.

• From address must match exactly what you entered when starting the test
• Placement ID must appear in the message body (snippets are provided on the test page)
• Send to every seed address in the assigned list
• Use the same subject and content you want to evaluate (marketing vs transactional)

Four-hour validation window

Four hours because senders routinely paste the Placement ID into a campaign and send it an hour or two later. A shorter window recorded those seeds as delivery failures for mail that had not been sent yet. If you send later still, or delivery is slow:

• Click Check now (Recheck) on the test page: reopens the check window using the same Placement ID and seed list
• Resend your email if needed, then run Check now again
• Recheck does not charge an additional test credit

You can also refresh the test page while the window is open to see live updates as seeds are found.

Reading results

Each test shows:

• Inbox rate: percentage landing in Primary Inbox
• Breakdown: Inbox, Promotions, Updates, Social, Spam, Missing per seed
• Per-seed detail: open any test for folder-level results by mailbox provider

Missing usually means the message never arrived, arrived after the window closed, or the Placement ID was not found in the body. Double-check From address, seeds, and ID before rechecking.

Credits and plans

Each new test costs one credit from a monthly allowance set by your plan; higher tiers may be unlimited. The allowance resets on your billing date rather than on the 1st of the month, and unused credits do not carry over. Your balance appears in the Inbox Intelligence header, and Placement Logs shows the history.

A credit is spent when the test is created, not when your mail arrives, and deleting a test does not return it. Rechecking an existing test is always free. See plan and billing.

Providers covered

Seed mailboxes cover Gmail, Google Workspace, Microsoft 365, Yahoo, Zoho and AOL. Every test draws from the pool available at the time it starts, so the seed list on the test itself is the authoritative answer for that run rather than this page.

The mix matters when you read a result. A weak score driven entirely by one provider is a different problem from a weak score spread evenly, and the per-provider breakdown on the result is where you tell them apart.

Tips for accurate tests

• Run tests from the same IP and authentication setup you use for production campaigns
• Test both cold and warmed domains separately: reputation differs
• Compare HTML vs plain-text variants if content filtering is a concern
• Pair placement tests with deliverability checks and sender reputation for full context

Why it landed where it did

A placement test tells you where the message went. The Content Analysis tab on each completed test tells you why: it reads the copy that was actually delivered to a seed mailbox along with the route it took, and reports the sending path and the copy separately.

That separation matters, because the two fail independently. A message can be well written and still not arrive, if reverse DNS is missing or the server announces itself as a bare IP address. The documentation covers every figure on that report, including what the spam filter score means and where the report stops being reliable.

Content analysis → · DNS setup for Inbox Boost → · Start Inbox Boost →