What does “too many connections” mean?

Too many connections indicates connection limits exceeded:

What it means:

You have more simultaneous SMTP sessions than allowed. The server is limiting concurrent connections per sender. Additional connections are being rejected.

Why limits exist:

Resource management: Servers have finite connection capacity. Fair usage: Preventing one sender from monopolizing resources. Abuse prevention: Limiting potential spam impact.

Typical codes:

421 with "too many connections." "Connection refused" at connection time.

Response:

Reduce concurrent connections to this server. Queue messages and send sequentially. Use connection pooling efficiently. Check ESP configuration for connection limits.

Too many connections means the dock is full. Wait for berths to clear before sending more ships.