Live check of every MX host: opens TCP 25, runs EHLO + STARTTLS, validates TLS certificate trust chain, hostname match, expiry window, advertised EHLO capabilities, plus PTR and forward-confirmed reverse DNS. Read-only — connects and quits without sending mail. Returns per-MX cipher/version, cert...
AI agents call check_smtp_tls to retrieve information from Intodns without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs live diagnostic checks of SMTP TLS configuration by connecting to mail servers and retrieving certificate, cipher, and DNS information. While it initiates network connections, it makes no modifications to data, sends no mail, and takes no actions beyond querying and validating existing configurations. It is purely informational/diagnostic in nature, making it a Read operation.
From the tool's definition Tool description explicitly states 'Read-only — connects and quits without sending mail' and 'opens TCP 25, runs EHLO + STARTTLS, validates TLS certificate trust chain' with no modifications to any systems.
Risk signalsBulk/mass operation — affects multiple targets
Attacks that exploit this kind of access
Live check of every MX host: opens TCP 25, runs EHLO + STARTTLS, validates TLS certificate trust chain, hostname match, expiry window, advertised EHLO capabilities, plus PTR and forward-confirmed reverse DNS. Read-only — connects and quits without sending mail. Returns per-MX cipher/version, cert SANs, expiry days, FCrDNS verdict, and STARTTLS-required flag. Use to verify inbound mail TLS posture; pair with check_mta_sts for the policy layer. May be slower (10-30s) due to live SMTP handshakes. No auth. It is categorised as a Read tool in the Intodns MCP Server, which means it retrieves data without modifying state.
Register the Intodns MCP server in PolicyLayer and add a rule for check_smtp_tls: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Intodns. Nothing to install.
check_smtp_tls is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the check_smtp_tls rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for check_smtp_tls. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
check_smtp_tls is provided by the Intodns MCP server (rosconl/intodns-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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