Soft Bounce

What is it?

What is it?

A "Soft Bounce" refers to a temporary failure in delivering an email message to the recipient's mailbox, resulting from issues that are typically transient and may be resolved upon subsequent delivery attempts. Soft bounces are distinct from hard bounces, which indicate permanent delivery failures due to undeliverable or invalid recipient addresses.

Key points to remember

Key points to remember

  • Temporary Delivery Failure: Soft bounces occur when an email message cannot be delivered to the recipient's mailbox temporarily due to reasons such as the recipient's mailbox being full, the email server being temporarily unavailable, or the message size exceeding server limits.

  • Retry Mechanism: Email servers typically retry delivery of soft-bounced messages automatically over a defined period, making multiple attempts to deliver the message until it is either successfully delivered or the bounce becomes a hard bounce due to repeated failures.


  • Common Causes: Soft bounces can be caused by transient issues such as temporary network congestion, server downtime, mailbox overcapacity, or temporary DNS resolution problems, which may resolve themselves without intervention.


  • Handling Soft Bounces: Email senders should monitor soft bounce rates and take appropriate actions, such as adjusting sending frequency, optimizing email content, or temporarily pausing delivery to addresses experiencing soft bounces, to improve deliverability and mitigate potential issues.


  • Differentiation from Hard Bounce: Unlike hard bounces, which indicate permanent delivery failures due to invalid or non-existent recipient addresses, soft bounces are typically temporary and may resolve themselves upon subsequent delivery attempts, making them less severe regarding email deliverability impact.

Example of Use

Example of Use

  1. Mailbox Quota Exceeded: An email message soft bounces because the recipient's mailbox has exceeded its storage quota, preventing new messages from being delivered until the recipient frees up space.


  2. Temporary Server Error: A soft bounce occurs due to a temporary server error or maintenance downtime experienced by the recipient's email server, causing the server to reject incoming email messages temporarily until the issue is resolved.

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