Knowledge base
Channels and deliverability: getting the message there
A channel is the medium a message travels on. Platforms differ less on the list of channels and more on getting one of them, email, to actually land in the inbox. Both halves matter.
7 min read · Updated June 28, 2026
The channels
A cross-channel platform reaches people across several mediums. They differ by where the message appears, whether the app or site has to be open, and what consent each requires.
| Channel | Appears | Needs |
|---|---|---|
| Inbox, any time | Email address and consent | |
| SMS | Text inbox, any time | Phone number and explicit opt-in (regulated) |
| Mobile push | Lock screen, even when the app is closed | OS opt-in and a vendor SDK |
| In-app message | Inside the app, only while it is open | No OS permission |
| Web push | Browser, even when the site is closed | Browser opt-in |
| Embedded | Inline inside your own app or site UI | A vendor SDK |
Push is not in-app
The single most common channel mix-up: mobile push and in-app messages are different things. Push fires to the device even when the app is closed, delivered through the operating system, and requires the user to grant OS-level permission. An in-app message only renders while the user is actively inside the app, needs no OS permission, and waits for the next session.
Why it matters
Push and in-app are complementary, not interchangeable. Push pulls a lapsed user back; in-app guides a user who is already there. Confusing them leads to wrong expectations about timing and opt-in, and weaker results than using both together.
Deliverability: sent is not delivered is not inboxed
For email especially, getting a message accepted by the receiving server is not the same as getting it into the inbox. Three states, not one: sent (you handed it off), delivered (the server accepted it and did not bounce it), and inboxed (the server trusted it enough to place it in the primary inbox rather than the spam folder). You can measure the first two; the receiver decides the third.
Inbox placement comes down to a few levers:
- Sender reputation: the biggest factor, earned over time from your domain and IP sending history.
- Authentication: SPF lists which servers may send for your domain, DKIM cryptographically signs the message so it cannot be altered, and DMARC ties those to your visible From address and tells receivers what to do on failure.
- List hygiene: removing invalid and unengaged addresses; a high bounce rate is a red flag to mailbox providers.
- Engagement: opens, clicks, and replies signal wanted mail; spam complaints poison reputation fast.
The bar moved in 2024
Gmail and Yahoo now effectively require bulk senders to pass SPF, DKIM, and DMARC and to keep the spam-complaint rate under roughly 0.1 percent. Authentication is necessary but not sufficient: it gets you to the gate, while reputation and engagement decide inbox versus spam.
Frequently asked questions
Does sending on more channels always help?
No. The value is reaching each person on the channel they actually engage with, not blasting all of them. Over-messaging across channels drives opt-outs and spam complaints, which hurt deliverability.
What is the difference between SPF, DKIM, and DMARC?
SPF authorizes which servers can send for your domain. DKIM signs the message so tampering is detectable. DMARC ties both to your visible From address and sets a policy for what receivers should do when a check fails.
Why did my email send but not arrive in the inbox?
Delivered only means the receiving server accepted it. It may have been filed in spam. Inbox placement depends on sender reputation and engagement, not just successful delivery.
Keep reading
Sources
Part of the MarTech and customer engagement field notes on this site. Written by Antoni K Pestka.