Custom sending domains: setup, warmup, and multiple domains
Last updated July 24, 2026
In short. Add your domain under Settings → Sending, publish the DNS records, and verify. New domains warm up over 21 days (100, then 500, then 2,000 sends per day). Business verifies up to five domains, each with its own From name, and every campaign picks which one to send from.
A custom sending domain puts your own domain on platform sends (broadcasts and platform-routed mail) instead of the shared SEMAOS domain, so you build and own your sending reputation. Every paid tier includes at least one custom domain; Business verifies up to five. The Free tier uses the shared platform domain, but a trial can verify its own domain. Proving that mail from your domain lands is the main thing a trial is for, and the trial's flat send cap keeps it safe. Setup lives under Settings → Sending.
How do I set one up?
Add your domain and SEMAOS generates the DNS records to publish at your DNS host: CNAME records for DKIM signing, plus an MX and a TXT record for the custom MAIL FROM subdomain. Copy each record exactly (the page has one-click copy for each), publish them, then hit Check status. Verification usually completes within a few minutes of the records propagating, though DNS changes can occasionally take longer. The status badge on the page tracks each record.
Two practical notes. First, publish the records at whatever DNS host serves your domain, which is not necessarily your registrar. Second, if your domain already sends email elsewhere, these records add to what's there; they don't replace your existing mail setup.
What is warmup, and why can't I skip it?
Inbox providers judge sending domains largely by history, and a brand-new domain has none. A domain that goes from zero to thousands of emails on day one matches the signature of a spammer on a fresh domain, so providers junk it preemptively. Warmup builds the history gradually: SEMAOS caps a new custom domain's daily platform sends, and the cap climbs through three steps over 21 days.
The step you're on is the more cautious of two things: how long the domain has been verified, and how much it has actually sent. Age alone doesn't clear it. A domain that was verified weeks ago but has barely sent stays at a lower step until its real volume catches up, because reputation is earned by volume, not by the calendar. Sends beyond a day's allowance aren't lost; they wait and go out the next day. When volume is the thing holding you back rather than the calendar, the warmup banner says so directly and shows the count — "400 of 800 sends to the next step" — so you can see exactly how much sending lifts the cap. Once the domain has both aged past the schedule and sent enough to earn it, it sends at your plan's normal limits. The schedule is not adjustable, and that's deliberate: it's the floor below which warmup stops being credible to providers.
Does warmup affect my mailbox sends?
No. Warmup governs the platform channel only. Your connected Gmail or Outlook mailbox has its own established reputation and its own 400-per-day cap, so 1:1 and sequence sending continues at full speed while a new custom domain warms up. Running both in parallel is the intended pattern for a new account: mailbox for outreach now, custom domain warming in the background for broadcasts later.
Can I send from more than one domain?
On Business, yes: verify up to five sending domains. Every other paid tier verifies one. This is built for teams that run more than one brand or region from a single account. Each domain warms up on its own 21-day clock, so verifying a second domain doesn't reset the first.
Each verified domain carries its own sender identity: a From name and a From address you set on the domain's card under Settings → Sending. Recipients of a send from that domain see that name, not your account default.
Every broadcast, one-off send, and sequence picks which verified From to send from. A sequence uses one From for all of its steps. If you don't pick one, the send uses your account default. Leave a domain's identity fields blank and it falls back to that default too, so you only fill them in for the brands that need a distinct name.
If you remove a domain, or downgrade below the number of domains you've verified, campaigns pinned to a domain you no longer have don't fail. They fall back to your default sending address so mail keeps going out. Set the domain you care about most as your default before a downgrade takes effect, and it's the one that's kept.
When should I add a custom domain?
Before you need it, because of the 21-day clock. The product nudges you toward one after sustained platform sending on the shared domain, but the better move is starting verification the week you sign up if you know broadcasts are in your plans. A domain verified in week one is fully warmed by week four. If you're on Business and plan to run several brands, verify each one early for the same reason.