HELO is the correct opening for a classic SMTP session (and if you're using extended SMTP it's EHLO)

See RFC 821 for the details of the protocol. It's fairly simple and imo not a bad protocol to start with if you're trying to roll your own client for educational purposes.

In reply to Re^2: Sending e-mail problem by Crackers2
in thread Sending e-mail problem by Anonymous Monk

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