An ImprovMX alternative for code that has to read the mail

ImprovMXis an email forwarding service. You point your domain’s MX record at it, define aliases like hello@yourdomain.com, and mail sent to those aliases is forwarded to a mailbox you already read — Gmail, Fastmail, whatever you use. Paid plans add SMTP credentials so you can send replies that appear to come from the alias rather than from your personal address.

For that job it is a good product, and it is worth saying so plainly on a page like this one: it is inexpensive, it has been doing the same thing for years, and there is very little to configure. Thousands of small businesses run their entire mail identity on it.

The reason people end up searching for an alternative is not that it forwards badly. It is that at some point the reader of the mail stops being a person.

A forwarding service’s contract is: a message arrives, a copy leaves. It is not holding onto the message, it has not taken it apart, and it has no opinion about what was in it. That is exactly right when the destination is a human inbox, and exactly wrong when the destination is code.

The wall usually shows up as one of these:

• You are parsing MIME in your own codebase. To act on the mail you forwarded, something has to log into the destination mailbox over IMAP, work out which messages are new, and decode multipart bodies and quoted-printable text. That is a stateful poller and a MIME parser, and both are now yours.
• Support tickets arrive as forwarded email. You wanted POST /tickets with a JSON body. What you have is a mailbox, and the gap between the two is a service you did not plan to write.
• An agent needs to read and answer mail. An LLM given IMAP credentials and a raw RFC 5322 message spends most of its context on envelope headers and quoted history before it gets to the sentence that matters.
• You need to know why a message never arrived. Forwarding is fire and forget by design. Once the copy has left, spam verdicts, SPF and DKIM results and the reason a downstream provider rejected it are not yours to query.

Read the ImprovMXcolumn as the answer to “can my code do this without me building something first”, not as a scorecard. Where it says partly, the capability exists but not in the shape an application wants.

The concrete difference is one HTTP request. Instead of a copy of the mail arriving in a mailbox, your endpoint is called with the message already taken apart:

{
  "event": "email.received",
  "email": {
    "id": "em_2f9c1a4b7d3e5601",
    "threadId": "thr_8b21c0f4a95d",
    "messageId": "<CAF9xq2@mail.example.com>",
    "from": "customer@example.com",
    "to": ["support@yourdomain.com"],
    "cc": [],
    "subject": "Invoice 4021 looks wrong",
    "text": "Hi — line 3 is billed twice…",
    "html": "<p>Hi — line 3 is billed twice…</p>",
    "attachments": [
      { "filename": "invoice-4021.pdf",
        "contentType": "application/pdf",
        "size": 84213 }
    ],
    "verdicts": { "spam": "PASS", "spf": "PASS", "dkim": "PASS" },
    "receivedAt": "2026-07-30T09:14:22.104Z"
  }
}

Three headers come with it: x-inboundr-event, x-inboundr-delivery-id for idempotency, and x-inboundr-signature, an HMAC over the body and a timestamp so your handler can prove the request came from us. Failed deliveries are retried with backoff, and the message stays fetchable over the REST API for its retention window, so an outage on your side is not a lost email.

If the reader is an agent rather than a handler, the same account also answers over the Model Context Protocol, and no webhook is involved at all:

# One endpoint, the same API key.
https://inboundr.net/api/mcp

Some of the tools the agent gets:
  list_emails     newest first; filter by address, thread or direction
  get_email       full bodies, attachment metadata, auth verdicts
  get_thread      the whole conversation, oldest first
  send_email      pass inReplyTo to answer inside the thread

That is the part no forwarding service can offer, because it requires having kept and parsed the message in the first place. See the MCP tools for the full list, or how to give an agent its own address for what to do with them.

Deliberately no price table here. Both products change their pricing and a stale figure on a comparison page is worse than none, so check theirs at the source and ours here.

What is worth knowing is the shape of each bill:

• ImprovMX prices per domain, with a free tier that forwards for one domain and paid tiers that add SMTP sending, more domains and higher limits. Volume is bounded by fair-use limits rather than metered.
• Inboundr prices per account with an included message allowance, then meters what you use beyond it. Domains are not the billable unit — messages are — so twenty domains on one account is not twenty subscriptions.

For a single domain forwarding a modest amount of mail to a person, forwarding is the cheaper answer and probably always will be. The comparison only tips when you would otherwise be paying an engineer to build the parsing, storage and retry layer that turns forwarded mail into something a program can use.

The cutover is a DNS change, and it can be done without a gap in coverage if you do it in this order:

1. 1Add the domain in the Inboundr console and copy the two records it shows you — one MX record and one DKIM record. Do not change your DNS yet.
2. 2Create the endpoint that will receive the mail. If you are replacing forwarding like for like, that is a forwarding endpoint pointed at the same mailbox; if this is the migration that motivated the move, it is a webhook.
3. 3Publish the DKIM record and wait for the domain to verify. This step touches nothing about delivery, so it is safe to do while ImprovMX is still live.
4. 4Replace the MX record. Mail already in flight follows the old record until resolvers pick up the change; a low TTL set an hour beforehand shortens that to minutes.
5. 5Send yourself a test message and confirm it arrives at the endpoint. The console shows the parsed message and the delivery attempt, so a failure here is visible rather than silent.
6. 6Leave the ImprovMX aliases in place for a few days. They cost nothing once the MX record no longer points at them, and they are your rollback.