421 4.3.2 System not accepting network messages

Meaning

The host is not accepting messages.

Common causes

• Imminent shutdown.
• Excessive load.
• System maintenance.

How to fix

1. Retry later.

Example bounce

421 4.3.2 System not accepting network messages

Related codes

• 421 4.3.0 Temporary system problem
• 421 4.4.5 Server busy
• 421 Service not available