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Deliverability Letter

450 4.7.1

SFR_IN_103 Too Many SMTP Errors

Protocol Errors

The IP generated too many SMTP errors unrelated to other SFR_IN codes.

Mismatched TLS, invalid commands, or timeouts lead to SFR_IN_103. The IP is paused for two hours to protect the infrastructure.

Severity

WARNING

Provider

SFR

Reference

SFR_IN_103

Last Reviewed

2025-06-01

How to Fix 450 4.7.1

Follow these steps to resolve this SFR SMTP error and restore normal delivery.

  • Confirm your HELO/EHLO string is a valid, resolvable hostname.
  • Increase SMTP timeouts so the connection does not drop mid-session.
  • Avoid testing scripts that intentionally send malformed commands.
  • Limit retry attempts during the two-hour suspension window.

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