Sending channels: your mailbox vs. the platform

SEMAOS sends email through two different channels, and knowing which one a given email uses explains most of the product's behavior around limits, tracking, and deliverability. The routing is automatic. One-off emails and sequence steps go through the sending user's connected mailbox whenever one is connected. A From on one of your verified custom domains sends through SEMAOS from that domain instead. On a paid plan, they also go through SEMAOS, from your verified domain or the shared SEMAOS domain if you have none, when the sender has no working mailbox, and so does a sequence enrollment bigger than the mailbox can send in time. Choosing the shared SEMAOS address as the From doesn't take a send off a connected mailbox. Free sends only through the mailbox. Broadcasts always go through the SEMAOS platform.

Why two channels?

Because 1:1 outreach and bulk mail behave differently, and mixing them hurts both. An email that leaves your own Gmail or Outlook account looks to the recipient's provider exactly like any personal email you wrote by hand, which gives a sales email the best chance of reaching the inbox. Bulk mail can't ride that channel without burning it: providers cap personal accounts at a daily limit, about 500 for consumer Gmail (Gmail's limits) and lower for Outlook.com non-subscribers and new accounts (Outlook.com's limits), and get suspicious quickly. Bulk mail also has its own rulebook: Google's sender guidelines require anyone sending more than 5,000 messages a day to Gmail accounts to authenticate with SPF, DKIM and DMARC and to offer one-click unsubscribe on marketing mail. The platform channel absorbs the bulk work on infrastructure built for volume, with its own reputation management.

What routes where?

	Your mailbox	SEMAOS platform
One-off emails	Yes, when connected	Custom-domain From, or no working mailbox (paid)
Sequence steps	Yes, when connected	Custom-domain From, no working mailbox (paid), or a large enrollment (paid)
Broadcasts	Never	Always
Volume limit	250 to 1,000 per mailbox per day, by kind of account	Monthly plan pool
From address	Your connected address	Platform or custom domain
Open/click tracking	Off by default (opt-in)	Always on
Replies	Your inbox; auto-detected on Outlook	Your Reply-To address; with none set, your account admin
Available on Free	Yes	No

A platform send always has somewhere for replies to go. If you set a Reply-To address under Settings → Sending, that is where they land. If you leave it blank, the send carries your account admin's email as its Reply-To instead — on the shared SEMAOS domain and on your own verified domain alike. That second case matters more than it sounds: a dedicated sending subdomain such as mail.yourcompany.com usually has no mailbox, so without this a reply would simply bounce. Settings → Sending names the exact address a blank Reply-To resolves to.

If a sender has no connected mailbox, or the connection hiccups at send time, one-off and sequence sends fall back to the platform channel rather than failing (on paid plans and trials; the Free tier is mailbox-only). A one-off email sent from a mailbox you picked that isn't your default never falls back: if that mailbox can't send, the email isn't sent, because it would otherwise leave from an address you didn't choose. A fallback send follows all the platform rules: it counts against the monthly pool and carries tracking.

Can I choose the channel for a sequence or one-off?

Yes, through the Send from address. Leave it on your connected mailbox (the default) and the email sends from your inbox. Pick one of your verified custom domains instead, and it sends from that domain through SEMAOS, with the domain's own warmup and reputation rather than your personal inbox. A custom domain is the choice to make when the email should carry a branded address instead of a rep's own.

There is one exception for one-off emails. If your mailbox address is itself on one of your verified domains (jane@acme.com with acme.com verified), a one-off from that address goes out through SEMAOS from the domain, including the default pick, and counts like any platform send. The picker labels it "Via SEMAOS from acme.com". A sequence left on the default still sends from your mailbox in that case, because the default picks no address for SEMAOS to send from.

With a mailbox connected, the picker offers your mailbox and the domains you have verified. It leaves out the shared platform address, because a 1:1 email lands better from your own inbox or your own domain than from a shared one. Without an active mailbox (none connected, or one that needs reconnecting), on a paid plan or a trial, your sends go through SEMAOS anyway, so the picker also offers your default address and the shared platform address. Sequences and one-off sends use the same picker. If you pick a domain still inside its warmup window, the composer shows that day's remaining cap.

What happens if I enroll a list bigger than my mailbox can send?

The whole enrollment moves to the platform channel. When you enroll, SEMAOS compares the list size against what the sending mailbox has left for the day, which is its daily cap (250 to 1,000, depending on the kind of account) minus what it has already sent. If the list is larger, every step of that enrollment sends through the platform from your verified sending domain, or from the shared platform domain if you have not verified one of your own. The enroll screen tells you which before you commit.

Say you enroll 2,000 contacts. Your mailbox would need five days to work through them, so SEMAOS sends the list from your domain instead and it goes out in one pass, under that domain's warmup cap.

SEMAOS decides this once, at enrollment, and the choice holds for every step. A contact will not send from your inbox on step one and your domain on step three. Lists that fit inside your remaining budget stay on your mailbox and nothing about them changes.

Free has no platform sending, so an oversized list stays on your mailbox there. The overflow spreads across the following days as your cap resets, and SEMAOS still sends every message rather than discarding the excess.

A newly connected mailbox works up to its daily cap over its first three weeks (Connecting your mailbox has the numbers), so while it ramps up a smaller list can be over its budget. On a paid plan that list moves to the platform channel as above. On a trial it stays on the mailbox and spreads over the following days, the way it does on Free, so it doesn't use up the trial's platform sends.

Which limits apply to which channel?

Mailbox sends are governed by one number per mailbox, its daily cap: 250 a day for a personal Outlook account, 400 for a personal Gmail account, and 1,000 for a Google Workspace or Microsoft 365 account. Queued work resumes the next day. They are never metered against your monthly plan pool, on any tier. The one exception is a sequence enrollment larger than that day's remaining budget, which moves to the platform channel instead of queueing (see above).

Platform sends are metered against the monthly pool (7,500 on Solo up to 200,000 on Business) and pass the platform's deliverability gates: domain verification, the warmup schedule on a new custom domain, and the bounce-rate guardrails. None of those gates apply to mailbox sends, because that mail rides your own account's standing rather than shared infrastructure.

How do I tell which channel a send used?

The send's detail view shows the From address the email went out with. It doesn't name the channel, so go by the From: if it's your connected mailbox address, it was a mailbox send; if it's your custom domain or the platform domain, it went through the platform. The exception is a mailbox address on one of your verified domains. There, a one-off went through the platform, and a sequence step on the default went through your mailbox.

For the mailbox channel's mechanics (the cap, reply detection, tracking toggles), see connecting your mailbox. For the platform side, see custom sending domains and deliverability.