Proton MCP Server

Instructions

Implementation Reference

• src/tools/send.ts:26-61 (handler)

  The handler logic for the 'proton_send_email' tool, which validates input parameters and calls the 'sendMail' service to send an email via SMTP.

  async (params: z.infer<typeof SendEmailSchema>) => {
    try {
      // Ensure to, cc, bcc are arrays
      const toArray = Array.isArray(params.to) ? params.to : [params.to];
      const ccArray = params.cc ? (Array.isArray(params.cc) ? params.cc : [params.cc]) : undefined;
      const bccArray = params.bcc ? (Array.isArray(params.bcc) ? params.bcc : [params.bcc]) : undefined;
  
      const messageId = await sendMail({
        from: PROTON_USER,
        to: toArray,
        cc: ccArray,
        bcc: bccArray,
        subject: params.subject,
        text: !params.html ? params.body : undefined,
        html: params.html ? params.body : undefined,
      });
  
      return {
        content: [
          {
            type: 'text',
            text: `Email sent successfully!\nMessage ID: ${messageId}\nTo: ${toArray.join(', ')}\nSubject: ${params.subject}`,
          },
        ],
      };
    } catch (error) {
      return {
        content: [
          {
            type: 'text',
            text: `Error sending email: ${error instanceof Error ? error.message : String(error)}`,
          },
        ],
      };
    }
  }

• src/tools/send.ts:13-62 (registration)

  Registration of the 'proton_send_email' tool in the MCP server.

  server.registerTool(
    'proton_send_email',
    {
      title: 'Send Email',
      description: 'Send a new email. Supports plain text and HTML formats. Recipients can be a single string or array of strings.',
      inputSchema: SendEmailSchema,
      annotations: {
        readOnlyHint: false,
        destructiveHint: false,
        idempotentHint: false,
        openWorldHint: false,
      },
    },
    async (params: z.infer<typeof SendEmailSchema>) => {
      try {
        // Ensure to, cc, bcc are arrays
        const toArray = Array.isArray(params.to) ? params.to : [params.to];
        const ccArray = params.cc ? (Array.isArray(params.cc) ? params.cc : [params.cc]) : undefined;
        const bccArray = params.bcc ? (Array.isArray(params.bcc) ? params.bcc : [params.bcc]) : undefined;
  
        const messageId = await sendMail({
          from: PROTON_USER,
          to: toArray,
          cc: ccArray,
          bcc: bccArray,
          subject: params.subject,
          text: !params.html ? params.body : undefined,
          html: params.html ? params.body : undefined,
        });
  
        return {
          content: [
            {
              type: 'text',
              text: `Email sent successfully!\nMessage ID: ${messageId}\nTo: ${toArray.join(', ')}\nSubject: ${params.subject}`,
            },
          ],
        };
      } catch (error) {
        return {
          content: [
            {
              type: 'text',
              text: `Error sending email: ${error instanceof Error ? error.message : String(error)}`,
            },
          ],
        };
      }
    }
  );

• src/schemas/index.ts:35-42 (schema)

  Zod schema definition for 'proton_send_email' inputs.

  export const SendEmailSchema = z.object({
    to: z.union([z.string(), z.array(z.string())]),
    cc: z.union([z.string(), z.array(z.string())]).optional(),
    bcc: z.union([z.string(), z.array(z.string())]).optional(),
    subject: z.string(),
    body: z.string(),
    html: z.boolean().default(false),
  });

• src/services/smtp.ts:41-65 (helper)

  Service function that handles the actual SMTP email sending using nodemailer.

  export async function sendMail(options: MailOptions): Promise<string> {
    const transporter = getTransporter();
  
    const mailOptions = {
      from: options.from || PROTON_USER,
      to: options.to,
      cc: options.cc,
      bcc: options.bcc,
      subject: options.subject,
      text: options.text,
      html: options.html,
      headers: {} as Record<string, string>,
    };
  
    // Set threading headers if provided
    if (options.inReplyTo) {
      mailOptions.headers['In-Reply-To'] = options.inReplyTo;
    }
    if (options.references) {
      mailOptions.headers['References'] = options.references;
    }
  
    const result = await transporter.sendMail(mailOptions);
    return result.messageId || 'success';
  }