What is the Difference between Hard and Soft 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.
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)
For soft bounces (blocks), we will attempt to re-send the messages for up to 72 hours. Undeliverable users who only return soft bounces are periodically unsubscribed as though they were a hard bounce.
Through Sendgrid (our SMTP technical partner), you have an option to turn on Bounce notifications and have these forwarded to your own address. (not recommended for large senders unless there is a dedicated high-volume inbox)