What the receiver is telling you

A temporary refusal at the recipient stage. Greylisting is the overwhelming cause and clears on retry. The unverified-address form means the receiver is a relay that checks recipients against a backend it could not reach; it also clears. Temporarily disabled mailboxes usually mean an account in transition. Retries handle all of these.

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. Nothing for the first few retries.
2. If a specific address keeps returning 450 for days, treat it as a soft bounce and remove after three failures.
3. If it is unverified-address on every recipient at one company, their relay's backend is down; wait.

don't Do not remove on the first 450. Greylisting looks exactly like this.

Decode the whole bounce

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

Common questions