4 min read
Hard vs soft bounces
A hard bounce means the address does not exist; it is suppressed automatically and permanently. A soft bounce is temporary — a full mailbox or a busy server — and is retried before being given up on.
Complaints
A complaint is a recipient marking your message as spam. Complaints suppress the contact immediately. A sustained complaint rate above roughly 0.1 percent puts your sending at risk.
The usual causes are purchased lists, infrequent sending and a hard-to-find unsubscribe link. Fix the cause, not the symptom.