A clean list sent from a cold mailbox still lands in spam
Deliverability has two halves. One is who you send to, and checking the list before you send covers it. The other is what you send from, and it gets far less attention, because nothing about it is visible from inside a campaign.
Mailbox providers judge the sender before they read the message. Is the domain authenticated? Has this mailbox built up a history of ordinary mail, or did it appear last week and start writing to strangers? Is it throwing errors? A campaign started on a mailbox that only just finished warming, or on a domain whose DKIM record broke when somebody moved the DNS, does not fail loudly. Nothing bounces. There is no error. The mail goes to spam, the replies do not come, and you blame the copy.
This play is the check you run while the campaign is still idle. It reads the state of every mailbox you plan to use and tells you which ones should carry the send and which should sit it out.
What you get back
One row per mailbox: go or no-go, the reason in plain words, its state, its warm-up status and where warm-up mail has been landing, and the four authentication records. One row per domain, because a failing record takes every mailbox on that domain with it. The bounce picture from your recent campaigns. And a capacity line: what the go mailboxes can send in a day between them, against the size of the list.
Nothing is started, paused or edited.
Variations worth knowing
Run the placement test. On SendKit the agent can create an inbox placement test, which sends seed mail from your mailboxes and reports where it landed. It asks first, and it reads past results for free.
Not on SendKit. Paste what your tool shows for warm-up and domain records, and the same rules produce the same verdicts.
Then build. With the go mailboxes named, build the outreach sequence and attach only those.
Where this goes wrong
A go is a snapshot. It describes the mailbox on the day it was read. If the campaign slips by a month, check again.
Warm-up complete is not a licence for full volume. A mailbox that has only ever sent warm-up mail should ramp up, not open at its daily maximum.
One domain, one reputation. Ten healthy mailboxes on a domain with a failing DMARC record are ten no-gos. Fix the record first.
Sending from the domain your clients write to. If campaign mailboxes share a domain with your everyday email, damage to one reaches the other.
Passing every check with a bad message. Healthy mailboxes do not protect you from complaints. The check says nothing about whether the reader wanted the email.
