What the receiver is telling you

Your server queued the message and retried it — usually for one to three days — and never got a definitive answer. The recipient's MX was down, was greylisting without ever letting it through, was deferring on rate (4.7.x) continuously, or the connection kept timing out. The message is now abandoned. It tells you the destination was unreachable for the whole window, which for a real business domain is rare and worth a look.

How to handle a soft bounce

Your server or sending tool retries soft failures automatically, usually for one to three days. Most clear on their own. The mistake is leaving an address that soft-bounces on every step in an active sequence: each attempt is logged, and a mailbox that has been full or unreachable for two weeks is not going to read a follow-up. Three consecutive soft failures is the point to remove it. Track soft bounces separately from hard ones; they are a different signal and receivers weight them differently.

What to do

1. Check the recipient domain's MX now. If it resolves and answers, the outage was temporary — resend once.
2. If your whole send to one provider expired, you were being rate-limited for days: reduce volume to that provider and check for a reputation block.
3. If it happens across many unrelated domains at once, the problem is on your side — a broken outbound queue or a blocked port 25.

don't Do not treat it as a bad address on its own. It says nothing about whether the mailbox exists.

Decode the whole bounce

Paste the complete failure notice — every code and the receiver's wording — and get each part explained together.

Common questions