Soft bounce (email)
What is Soft bounce (email)?
A soft bounce is a temporary email delivery failure — the receiving server couldn't accept the message right now, usually because the recipient's mailbox is full, the server is briefly unavailable or greylisting, or a throttle rate-limits new connections — but the address itself is valid and the same message may succeed on a later attempt. Sending platforms retry the message for a bounded validity window; if the retries never deliver, the message is closed as expired and the address is treated as a hard-bounce candidate for suppression.
More detail
The transient causes differ from the retry loop's perspective: a full mailbox or a momentarily unreachable server resolves itself, while a greylisting or content-related defer is the recipient's anti-spam layer putting a new sender through a probation window — a well-configured sender should pass on the next attempt. The opposite failure mode is the address that never resolves on any number of retries, which is how a soft bounce eventually hard-fails.
Orbit's email delivery loop keeps a soft bounce in the retry queue — the recipient server gets multiple acceptance chances across the validity window — and only then closes the message as expired and feeds the address toward suppression. A soft bounce that converts to delivered is recorded as a normal delivery event on the dashboard, so the campaign's bounce metric only counts the addresses the retry loop ultimately gave up on.
Frequently asked
- How is a soft bounce different from a hard bounce?
- Permanence. A soft bounce means the recipient server had a temporary issue — a full mailbox, a brief outage, a greylist probation window — and the address itself is valid, so the platform retries. A hard bounce means the failure will recur identically on every retry — the address doesn't exist, the domain doesn't resolve, or the server refuses your sender outright — so the correct response is suppression, not another attempt.
- How many times should a soft bounce be retried?
- Within the platform's bounded validity window — a handful of spread-out retries over a period measured in hours, not an open-ended loop. If the message still hasn't delivered when the window closes, it's logged as expired and the address becomes a suppression candidate, because an indefinite retry is still a deliverability risk that masquerades as temporary failure.
- What are the most common soft-bounce causes?
- A full recipient mailbox, a recipient server that's briefly offline or rate-limiting new connections, greylisting from the server's anti-spam layer, or a message the receiving filter deferred on a content heuristic — all transient enough that a valid address can pass on a re-attempt within the validity window.
See also
Build it on Orbit
Voice, messaging, email, video, and AI agents on one platform and one pay-as-you-go bill. Start free — no credit card required.