4.7.0: temporarily refused on policy grounds

A 4.7.0 means the receiver is temporarily refusing your mail on policy grounds: most often greylisting, sometimes rate limiting or an unmet TLS requirement. Greylisting is normal. The first attempt from an unknown sender is refused and your server's retry arrives minutes later. If it persists, read the reason text and treat it as a reputation or TLS problem.

The error

451 4.7.0 Greylisted, please try again later

421 4.7.0 IP not in whitelist for RCPT domain, closing connection

What it means

The receiver is temporarily refusing your mail for policy reasons — most often rate limiting, greylisting, or a TLS requirement that was not met.

The receiver is refusing your mail because of how your sending IP or domain behaves, not because of this particular message.

Why it happens

Greylisting is the most common cause and the least alarming: the receiver deliberately refuses a first attempt from an unknown sender, because most spam software never retries. Legitimate mail arrives minutes later with no intervention.

How to fix it

1. Let the queue retry; greylisting clears on the second attempt.
2. Read the accompanying text — receivers put the actual reason there.
3. If it persists, treat it as a reputation or TLS configuration problem rather than a transient one.