What are Bounces and Blocks?

What is the difference between Hard and Soft Bounces?

Bounces:

Hard bounces occur when delivery is impossible and future deliveries are also impossible. This usually means

• The email address is invalid
• The email domain (website.com) is valid, but the recipient does not exist
• The email account is closed

Any hard bounced email will be unsubscribed.

Blocks:

Soft bounces (also known as blocks) occur when a delivery is not possible right now. This usually means:

• Recipient inbox is full
• Recipient inbox is over-loaded (too many messages at once)
• Mailbox provider (domain) is over-loaded (too many messages for server to process)
• Connection error
• Message rejected (blacklist)

Additional resources:

Email Bounce Management: Soft Bounces vs. Hard Bounces