[tannevaled]

Wires github.com/go-ruby-net-smtp/net-smtp — the MRI-byte-exact SMTP codec (command grammar, DATA dot-stuffing, reply parser, EHLO capability parse, SASL PLAIN/LOGIN/CRAM-MD5) — into rbgo so require "net/smtp" provides a native Net::SMTP with no .rb file.

Transport

The codec deliberately leaves out the socket, so — unlike the redis/pg bindings' injected-IO seam — the transport here is rbgo's real socket layer (socket.go): Net::SMTP#start dials a TCPSocket, wraps it in a smtpConn satisfying the library's Conn seam (WriteLine/ReadLine/WriteRaw/StartTLS), and drives netsmtp.Session against it exactly the way MRI drives its @socket. STARTTLS upgrades the same socket in place through the crypto/tls handshake the net/http transport already uses; implicit TLS (SMTPS, tls: true) wraps on connect. TLS defaults to VERIFY_NONE, matching the transport default (full cert-store verification is a follow-up).

Ruby surface bound

• Construction: Net::SMTP.new(addr[, port]), Net::SMTP.start(...) (block + non-block; positional and keyword credentials; tls: / starttls:), default_port / default_tls_port / default_ssl_port / default_submission_port
• Lifecycle: start / finish / started?
• Sending: send_message / sendmail, open_message_stream / ready (yields a puts/print/write/<< adapter), data (string or block)
• Low-level: ehlo / helo / mailfrom / rcptto / rcptto_list / rset, authenticate (:plain / :login / :cram_md5)
• Config & capabilities: esmtp? / esmtp=, enable_tls / enable_ssl / disable_tls, enable_starttls / enable_starttls_auto / disable_starttls, tls? / ssl? / starttls? / starttls_auto? / starttls_always? (exclusivity enforced), open_timeout / read_timeout, capable_starttls? / capable_plain_auth? / capable_login_auth? / capable_cram_md5_auth? / capable_auth_types
• A Net::SMTP::Response view (status / string / message / success? / continue?)
• The Net::SMTPError family (SMTPError < ProtocolError; ServerBusy / Syntax / Authentication / Fatal / Unknown / UnsupportedCommand), so a codec error rescues as its MRI-faithful class

ActionMailer's SMTPDelivery could now be backed by this — left as a follow-up (not wired here).

Wiring

registerNetSMTP() in the builtins bootstrap (after registerSocket/registerNetHTTP), providedFeatures["net/smtp"], classOf cases for the three new value types, mirroring the redis/pg/net-http split.

Tests

Tests drive an in-process scripted SMTP server (plaintext, STARTTLS-upgrade, and implicit-TLS variants using a generated self-signed cert) plus Go-level unit tests for the connless / nil-session branches — deterministic, no real network, goroutines joined on cleanup.

• 100% coverage of net_smtp.go + net_smtp_bind.go
• Full internal/vm + internal/object suites green (76.8s / 0.3s)
• gofmt -l empty, go vet clean, -race clean on the new tests
• Builds on all six 64-bit arches (amd64/arm64/riscv64/loong64/ppc64le/s390x)

CGO=0, GOWORK=off, go 1.26.4, BSD-3-Clause.

🤖 Generated with Claude Code

[tannevaled]

Superseded by the net-wave consolidation PR (single merge onto main; shared builtins/require/object_model). Work preserved verbatim; branch kept.