What the receiver is telling you

The mailbox exists and is active but has no room. Gmail says so with a temporary code, on the theory that the owner will delete something; Exchange and many hosted providers say it with a permanent one. For a cold sender the practical meaning is the same: this person is not reading mail, or they would have noticed the warning. A mailbox that stays full for weeks is abandoned.

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. Let the sending tool retry for a few days on the 4.2.2 form; most retry automatically.
2. After three consecutive over-quota bounces, remove the address — it is abandoned.
3. Do not count a single 5.2.2 as a hard bounce in your own metrics; it is a soft failure with a permanent code.

don't Do not keep sending a sequence into a full mailbox. Every follow-up bounces and each bounce is logged against your domain.

Decode the whole bounce

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

Common questions