Soft Bounce
A soft bounce is a temporary email delivery failure caused by issues like a full inbox, server downtime, or a message that exceeds size limits.
What Is Soft Bounce?
Soft bounces are usually transient problems. The email address is valid, but something prevented delivery at that moment. Common causes include the recipient's mailbox being full, the receiving mail server being temporarily offline, the email being too large, or the receiving server rate-limiting incoming messages. Most email platforms will automatically retry soft-bounced messages. However, addresses that consistently soft-bounce over multiple sends should be treated as effectively undeliverable.
Why It Matters for Newsletters
While a single soft bounce isn't alarming, recurring soft bounces from the same addresses inflate your bounce rate and waste sending resources. They can also mask list quality issues — an address that always soft-bounces is practically as useless as a hard bounce.
Best Practices
- Allow 2-3 retry attempts for soft bounces before suppressing
- Track addresses that soft-bounce repeatedly across multiple campaigns
- Suppress addresses after 3 consecutive soft bounces
- Monitor overall soft bounce rate — a spike may indicate a problem with your email size or content
How Aldus Handles This
Aldus tracks soft bounces per subscriber and automatically suppresses addresses after three consecutive delivery failures. This prevents wasted sends while giving temporary issues time to resolve.