For the solo founder

Main company. Side project.
The thing in stealth.

Solo founders typically run three or four sending identities at once — the main company, the side project, the stealth idea, the LLC. Folio puts each domain in one reading view while keeping its DKIM key, DMARC posture, and bounce reputation isolated, so a Product Hunt spike on the side project cannot burn down the main company's deliverability.

Every solo founder runs at least three things: the company on the business card, the side project they're probably shipping next quarter, and the experiment they haven't quite admitted to yet. Each has its own domain. Each needs its own sending reputation.

Folio is the inbox that keeps them separate where it matters — colour, signature, reputation — and together where it doesn't — one reading surface, one sign-in, one flat price.

Updated 11 May 2026 (2026-05-11)

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I · The problem with side projects on shared infrastructure

A stealth launch that burns your main domain.

The fastest way to torch a main company's sending reputation is to run a side project off the same domain. A surprise batch of beta invites, a Product Hunt launch, a press push — and suddenly your core domain is sitting in everyone's spam folder.

The usual fix is to buy a second domain and run it through Mailgun or Resend. Now you have two sending providers to configure, two DNS setups, and two places to check for bounces. Your inbox, though, is still one Gmail tab that routes to one From address.

The actual problem is not a sending problem. It's an inbox problem. You need the reputation boundary and the reading surface to be managed in the same place.

A side project shouldn't be able to burn down a main company's deliverability by accident. Most inboxes make it easy to.

II · Your morning, if it worked

Three companies, one reading view.

Not a screenshot — a live render in the same editorial design system the app uses. Each row's stripe is the domain the letter was sent to. Hover (or read quickly, by eye): which self is each one addressed to?

III · How Folio fits a solo founder's week

Separate reputations. One reading surface.

Every domain you bind is its own sending identity — its own DKIM key, its own DMARC posture, its own bounce tracking. Your main company's reputation can't be burned by a side project's Product Hunt spike, because the two domains don't share infrastructure you can see.

  • ·
    Three domains. One price. Solo — $2.99/mo billed annually (or $3.50/mo) — covers main, side, and stealth, up to 3 domains. When the fourth idea ships, Studio takes you to 10 and Holding Co. to unlimited.
  • ·
    Per-domain sending reputation. A bounce-storm on the side project's domain does not drag down the main company's sender score. Reputations stay siloed.
  • ·
    Auto-From on reply. A press request that arrived at hello@brush.stream replies from hello@brush.stream. You don't have to remember which self you were when you opened the letter.
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    Stealth stays stealth. Bind the stealth domain, give it an innocuous subdomain, route inbound through Folio. Nothing visible on your public profile ties them together.

IV · Pieces that matter when a launch lands

The things your launch day will test.

Launch day is when your email setup shows its seams. These are the pieces Folio handles without you having to think about them.

Per-domain DKIM
Each bound domain signs with its own RSA-2048 key. The signature a recipient's mail server verifies is scoped to that domain.
Bounce suppression
Dead addresses are marked at the edge. A 500-recipient Product Hunt announcement doesn't leave a trail of repeat-bounce penalties.
Threading headers
In-Reply-To and References are always set. Press replies fold cleanly into the journalist's original thread.
Magic-link sign-in
No password to manage during a 48-hour launch window. One-time, fifteen-minute links to the address you already check.

V · Common questions

Questions readers ask.

Will a side project's launch hurt my main company's deliverability?

No — provided each project is on its own domain. Folio signs every outgoing message with the DKIM key of the sending domain (per RFC 6376), so recipient mail servers evaluate reputation per domain rather than per account. A bounce spike or spam complaint on the side domain does not propagate to the main domain.

Can I run a stealth domain without it being publicly tied to my main brand?

Yes. Bind the stealth domain, route inbound through Folio with a private MX record, and nothing on your public marketing surface links the two. SPF/DKIM/DMARC are configured per-domain, so headers on outbound mail never reference the parent identity.

How is this different from Gmail's 'Send mail as' aliases?

Send-as routes every outbound message through Gmail's servers using a single shared reputation, which means one project's deliverability problem is every project's deliverability problem. Folio treats each domain as a first-class identity with its own DKIM key, SES sending principal, and reputation.

What happens to reply From addresses on a busy launch day?

Each incoming letter remembers which of your domains it was addressed to. When you hit reply, the From line is pre-filled to that domain — no toggle, no second-guessing. You can still override per message, but the default is correct.

Do I need to migrate my main inbox to start?

No. Many solo founders begin by binding only the side or stealth domain to Folio while leaving the main domain on its existing provider. Once you have a feel for the multi-identity flow, you can add the main domain — DNS-only, no mailbox migration required.

VI · Adjacent readers

Other shapes of the same problem.

VII · Sources & further reading

Where the claims come from.

Open the first letter

Ship the side project without the spam folder.

Fourteen days, no charge. Bind the main domain, the side domain, the stealth domain. Do a test send on each. See what a properly-isolated sending setup looks like — and watch it all arrive in one place.

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Updated 11 May 2026 (2026-05-11)