Plugins

A plugin is a function that receives the Fumi instance and registers its own handlers.

my-plugin.ts

import type { Plugin } from "@puiusabin/fumi";

export function myPlugin(): Plugin {
  return (app) => {
    app.onConnect(async (ctx, next) => {
      console.log(`[connect] ${ctx.session.remoteAddress}`);
      await next();
    });
  };
}

server.ts

import { Fumi } from "@puiusabin/fumi";
import { myPlugin } from "./my-plugin.ts";

const app = new Fumi({ authOptional: true });
app.use(myPlugin());
await app.listen(2525);

Bundled plugins

fumi ships a small set of reference plugins. Import them from @puiusabin/fumi/plugins/*.

logger

Logs each SMTP phase to stdout.

server.ts

import { logger } from "@puiusabin/fumi/plugins/logger";
app.use(logger());

denylist

Blocks connections from specific IP addresses.

server.ts

import { denylist } from "@puiusabin/fumi/plugins/denylist";
app.use(denylist(["1.2.3.4"]));

senderBlock

Rejects mail from specific sender domains.

server.ts

import { senderBlock } from "@puiusabin/fumi/plugins/sender-block";
app.use(senderBlock(["spam.example"]));

rcptFilter

Only accepts recipients whose domain is in an allowed list.

server.ts

import { rcptFilter } from "@puiusabin/fumi/plugins/rcpt-filter";
app.use(rcptFilter(["mycompany.com"]));

maxSize

Rejects messages that exceed a byte limit. Pair with FumiOptions.size.

server.ts

import { maxSize } from "@puiusabin/fumi/plugins/max-size";

const app = new Fumi({ size: 10_000_000 });
app.use(maxSize(10_000_000));

requireTls

Rejects MAIL FROM on unencrypted connections (STARTTLS not completed).

server.ts

import { requireTls } from "@puiusabin/fumi/plugins/require-tls";
app.use(requireTls());

Writing a plugin with options

Plugins are factory functions — return a Plugin from a function that takes options.

rate-limit.ts

import type { Plugin } from "@puiusabin/fumi";

export function rateLimit(opts: { max: number; windowMs: number }): Plugin {
  const counts = new Map<string, number>();
  return (app) => {
    app.onConnect(async (ctx, next) => {
      const ip = ctx.session.remoteAddress;
      const count = (counts.get(ip) ?? 0) + 1;
      counts.set(ip, count);
      if (count > opts.max) {
        ctx.reject("Too many connections", 421);
      }
      await next();
    });
  };
}

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