Bounces

Bounce, bouncing, and/or bounces generally refer to an undelivered email that is returned to the sender's server due to various reasons. Bounces are classified into two main categories: soft and hard.

Hard bounces typically indicate that the email address is invalid. Soft bounces typically indicate either that the recipients mailbox is full (yes this still happens) or that the ISP is rejecting mail due to exceeding rate limits or poor past engagement.

Proper warm up, list hygiene, and maintaining a strong reputation are crucial to maintaining a low bounce rate. Bounces can increase if there are issues with either domain or IP reputation.