Edit an existing draft email. Since JMAP emails are immutable, this atomically destroys the old draft and creates a new one with the updated fields. Only fields you provide will be changed; others are preserved from the original draft.
AI agents use edit_draft to create or update resources in Fastmail MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Fastmail MCP Server environment.
Although the description mentions 'destroys,' this is an implementation detail of the JMAP API's immutability constraint, not a user-facing destructive action. The tool's purpose is to modify draft emails, a reversible operation. Draft emails have not been sent and can be further modified or discarded, making this fundamentally a Write operation.
From the tool's definition Tool description states it 'atomically destroys the old draft and creates a new one with the updated fields.' While destruction occurs, it is limited to draft emails (unsent, non-persisted messages) and is reversible—the updated draft can itself be edited or…
Documented attack patterns abuse exactly the kind of access edit_draft gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Fastmail MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for edit_draft:
{
"version": "1",
"default": "deny",
"tools": {
"edit_draft": {
"limits": [
{
"counter": "edit_draft_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}edit_draft stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Edit an existing draft email. Since JMAP emails are immutable, this atomically destroys the old draft and creates a new one with the updated fields. Only fields you provide will be changed; others are preserved from the original draft. It is categorised as a Write tool in the Fastmail MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Fastmail MCP Server MCP server in PolicyLayer and add a rule for edit_draft: 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 Fastmail MCP Server. Nothing to install.
edit_draft is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the edit_draft 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 edit_draft. 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.
edit_draft is provided by the Fastmail MCP Server MCP server (madllama25/fastmail-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Fastmail MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
38 Fastmail MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.