Exact response pattern
220 Service readyInfoGenericProtocol
What it means
The receiving SMTP service is ready for a new session.
Likely causes
- Normal greeting after connection.
Recommended response
- Send EHLO or HELO and continue the SMTP transaction.
Operational rule: Preserve the complete SMTP response, remote hostname, sending IP, envelope sender and timestamp. Never diagnose from the three-digit code alone.