Test an SMTP server connection by attempting to connect and authenticate. If from_email and to_email are provided, the tool may attempt to send a test email. Only provide these fields if you are authorized to send from the account and intentionally want to test full sending capability.
Risk signalsAccepts URL/endpoint input (host) · Handles credentials or secrets (password)
Part of the MailX Email Deliverability server.
Free to start. No card required.
AI agents call smtp_check to retrieve information from MailX Email Deliverability without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though smtp_check only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"smtp_check": {}
}
}See the full MailX Email Deliverability policy for all 16 tools.
These attack patterns abuse exactly the kind of access smtp_check gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Test an SMTP server connection by attempting to connect and authenticate. If from_email and to_email are provided, the tool may attempt to send a test email. Only provide these fields if you are authorized to send from the account and intentionally want to test full sending capability.. It is categorised as a Read tool in the MailX Email Deliverability MCP Server, which means it retrieves data without modifying state.
Register the MailX Email Deliverability MCP server in PolicyLayer and add a rule for smtp_check: 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 MailX Email Deliverability. Nothing to install.
smtp_check 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 smtp_check 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 smtp_check. 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.
smtp_check is provided by the MailX Email Deliverability MCP server (https://themailx.com/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 16 MailX Email Deliverability tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.