A support desk on your own customer records, on the inbox you already use.

const mail = connection("resend", { description: "Sends replies from the support address." });

export const Ticket = entity("ticket", {
  description: "What the team decided about one support conversation.",
  properties: {
    conversationId: p.text({ unique: true, description: "The id in the inbox." }),
    customer: p.email({ description: "Who wrote in." }),
    subject: p.text({ description: "The conversation's subject." }),
    status: p.select(TICKET_STATUS, { default: "open", managed: true }),
    priority: p.select(PRIORITIES, { default: "normal", managed: true }),
    replies: p.integer({ default: 0, managed: true, description: "Replies sent so far." }),
  },
  relationships: {
    client: rel.one("client", { optional: true, inverse: "tickets" }),
    owner: rel.one(User, { optional: true, inverse: "tickets" }),
  },
}).actions((self) => ({
  reply: action({
    description: "Reply to the customer from the support address.",
    input: Schema.Struct({ ticket: self.ref, text: Schema.String }),
    connections: [mail],
    prepare: ({ input }) =>
      Effect.gen(function* () {
        const ticket = yield* self.get(input.ticket);
        const sent = ticket.replies + 1;
        // The email goes out even if the transaction fails, so its key comes
        // from the record: a retry reaches the same email, not a second one.
        const response = yield* mail.post("/emails", {
          headers: { "Idempotency-Key": `ticket:${ticket.id}:reply:${sent}` },
          json: { from: SUPPORT, to: ticket.customer, subject: `Re: ${ticket.subject}`, text: input.text },
        });
        if (!response.ok) {
          return yield* new ActionRejected({ message: "The reply was not sent." });
        }
        return { sent };
      }),
    handler: ({ input, prepared }) =>
      Effect.gen(function* () {
        const ticket = yield* self.get(input.ticket, { forUpdate: true });
        if (ticket.replies + 1 !== prepared.sent) {
          return yield* new ActionRejected({ message: "Someone replied first. Read the thread again." });
        }
        yield* self.update(ticket, { status: "waiting", replies: prepared.sent });
      }),
  }),
}));