Deliverability
What is Spam Complaint?
The event of a recipient marking a message as spam or junk, signaling the mailbox provider that the mail was unwanted.
A spam complaint occurs when a recipient clicks Report Spam or Junk in their mailbox, sending a negative reputation signal to the mailbox provider. Complaints are among the most heavily weighted reputation inputs, and where a feedback loop exists they are reported back to the sender. Sustained complaints push future mail to the spam folder and can ultimately trigger blacklist listings.
Why it matters for cold email
Cold email is unsolicited by nature, so it attracts complaints far more readily than opt-in mail, and even a small complaint share can damage domain reputation quickly. Tight targeting, easy opt-out, and low volume per inbox are the main levers for keeping complaints under provider thresholds.
Related terms
Stop guessing at deliverability.
Scheduler Zero handles authentication, warmup, and sender reputation so your cold email lands in the inbox, not the spam folder.