What the receiver is telling you

A temporary 'not now'. Gmail uses it when your sending rate or reputation trips a soft limit, greylisting servers use it for every first attempt from a new sender, and Exchange uses it for its own internal hiccups. Your server will retry. The question is whether the retries succeed: greylisting clears on the second attempt, an Exchange PRX error clears in minutes, and a Gmail rate limit clears only if you send less.

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. Greylisted in the text: nothing to do. The retry gets through.
2. Gmail unusual-rate text: reduce volume to Gmail immediately and check Postmaster Tools. If you keep sending, it becomes 5.7.28.
3. Exchange PRX text: transient on Microsoft's side; retries succeed.
4. If 4.7.0 persists for more than a few hours from one provider, treat it as a soft block on reputation.

don't Do not add more inboxes or a new domain to push past a Gmail rate limit. That converts a throttle into a block.

Decode the whole bounce

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

Common questions