Inbox placement
An SMTP 250 means the message was accepted, not that it reached the inbox. The placement test closes that gap the honest way: real sends to addresses you control, and what you saw, recorded.

Add the addresses you own, one on each provider you care about, with a label. They are yours, not a pool of strangers’ inboxes.
Pick an inbox, write a subject and a body as close to a real opener as you can, and the same message goes to every seed from that inbox. No send row, no lead, no tracking, no unsubscribe link: it has to look like the real thing to the filter, and it must not touch a campaign’s numbers.
Open each seed inbox and mark the result: inbox, promotions, spam or missing. The last twenty tests stay on the page, each with how many landed in the inbox at each provider, so a change over the weeks is visible.
Save the subject and body as a schedule, and while sending is running the same test goes out from every active inbox once every 7 days, or less often if you choose. An inbox without room under its cap or its domain’s is skipped that time, and the page says so.
Once every seed at a provider has a result and a smaller share landed in the inbox than on that inbox’s last complete test there, CraftNudge tells you by Telegram and by email, where those notifications are on.
These are real emails from a real inbox. They come out of that inbox’s daily cap and its domain’s number for the day, and the test is refused when either is spent.
Point your domain’s DMARC report address at an inbox you connect here, and the aggregate reports that arrive there are read as reports instead of being filed as replies. The summary sits on the same deliverability page.