421 4.3.0 Temporary system problem
Meaning
The receiving mail server is experiencing a temporary system problem or overload and cannot process the message right now.
Common causes
- The recipient's mail server is temporarily down or restarting.
- The receiving server is experiencing high traffic and is overloaded.
- There is a temporary network or routing issue preventing connection.
How to fix
- Do nothing immediately; your mail server should automatically retry sending the message later.
- If the issue persists for several days, check the recipient's domain for known outages.
- Verify your sending infrastructure is not sending mail too aggressively to a single provider.
Provider notes
Gmail. Often indicates 'Temporary System Problem. Try again later.'
Example bounce
421 4.3.0 Temporary System Problem. Try again later.
FAQ
- Do I need to resend the email?
- No, your mail server will automatically retry sending the email for a period (usually up to 72 hours).
- Is this a hard bounce?
- No, this is a soft bounce or deferral. The failure is temporary.