450 4.7.1
SFR_IN_107 Invalid HELO or Reverse DNS
SFR rejected the session because the HELO/EHLO name or reverse DNS is invalid.
SFR expects the connecting IP to have proper reverse DNS and to announce a matching hostname. Typos or generic cloud hostnames trigger SFR_IN_107.
Severity
WARNING
Provider
SFR
Reference
SFR_IN_107
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.
- ✓Set PTR records that map each IP to a descriptive, unique hostname.
- ✓Update the SMTP HELO string to match the reverse DNS value.
- ✓Avoid generic cloud hostnames like ip-10-1-1-1.compute.internal.
- ✓Document DNS changes so they survive infrastructure migrations.
Helpful Resources
More SFR SMTP Codes
Keep these related troubleshooting guides handy while addressing 450 4.7.1.
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