mail-mcp v0.1 — Rust MCP server for Sulkta email

Phase A: mail_send + mail_inbox_list + mail_inbox_read. Replaces
scripts/kayos_mail.py with a typed MCP server. Outbound guarantees Date,
Message-ID (own-domain), User-Agent, MIME-Version, multipart/alternative
for HTML+text, multipart/mixed for attachments, In-Reply-To +
References for threading.

Single account in v0.1 (default_account from config). Phase B adds
multi-account + threading + search; Phase C adds mark + attachments +
reply helper.

Stack: rmcp 0.1 (matches aldabra), lettre 0.11 + tokio-rustls, async-imap
0.10, mail-parser 0.9. Stderr-only logging (stdout is the MCP transport).

Smoke verified 2026-05-21: send -> land -> read kayos@sulkta.com round
trip, DKIM-Signature + Authentication-Results pass at the rspamd relay.

config.example.toml

@@ -0,0 +1,27 @@
+# mail-mcp config — copy to ~/.config/mail-mcp/config.toml, chmod 600.
+#
+# Passwords are NEVER inline. Each account names an env var (`password_env`)
+# AND a fallback file (`password_file`). Lookup order:
+#   1. env var
+#   2. shell-format file (`KEY=VALUE` per line)
+#   3. hard fail with a vault-pointer hint
+#
+# Vault canonical: bw.sulkta.com → "kayos@sulkta.com — IMAP/SMTP".
+
+default_account = "kayos"
+
+[accounts.kayos]
+from_name       = "Kayos"
+from_addr       = "kayos@sulkta.com"
+smtp_host       = "mail.sulkta.com"
+smtp_port       = 587
+smtp_starttls   = true
+imap_host       = "mail.sulkta.com"
+imap_port       = 993
+imap_tls        = true
+username        = "kayos@sulkta.com"
+password_env    = "KAYOS_SMTP_PASS"
+password_file   = "~/.config/kayos-mail/smtp.env"
+# Optional: pin Message-ID domain. Defaults to the part of `from_addr`
+# after the @ if unset.
+# message_id_domain = "sulkta.com"