The two-line definition
Deliverability is whether the receiving mail server accepts your message at all - it returns a 250 OK instead of bouncing or rejecting it. Placement (often called inbox placement) is what the provider does with the message after accepting it: inbox, Promotions/Updates tab, spam, or quietly dropped.
Deliverability gets you through the front door. Placement decides which room you end up in. A message can be 100% delivered and still never be seen.
Why the distinction matters
When someone says "my email is delivering fine," they usually mean their logs show no bounces. That only proves deliverability. The provider can accept every message and route all of it to spam - your bounce rate stays at zero while your open rate collapses. If you optimise for the number you can see (acceptance) you can make placement worse without ever noticing.
| Deliverability | Placement | |
|---|---|---|
| Question it answers | Was the message accepted? | Did it reach the inbox? |
| Decided at | SMTP time (the connection) | After acceptance, by the filter |
| Visible to the sender? | Yes - via the SMTP response / bounce | No - providers don't tell you |
| Driven mainly by | Authentication, DNS, reputation, blocklists | Engagement, content, sending history, complaints |
| Failure looks like | A bounce or rejection | Silence - mail "sent" but never read |
What drives deliverability
Deliverability is mostly mechanical, which is exactly why it's testable. A receiver decides whether to accept a connection based on things it can check in milliseconds:
- SPF, DKIM and DMARC - is the sender authenticated, and does it pass the domain's own policy?
- Reverse DNS and a sane EHLO hostname - does the sending server look legitimate?
- Blocklist status - is the IP known for abuse?
- MX records - can the domain receive replies and bounces?
- TLS - is the connection encrypted?
Get these wrong and you fail at the door: the message bounces or is rejected outright. Get them right and you've earned the right to be considered for the inbox - nothing more.
What drives placement
Placement is mostly about reputation and behaviour over time, and it's largely invisible. The big providers weigh signals no external tool can see from a single message:
- Engagement - do recipients open, reply, and move you out of spam, or delete without reading?
- Complaint rate - how often people hit "report spam." Gmail and Yahoo expect bulk senders to stay under roughly 0.3%.
- Sending history - consistent volume from a warmed-up domain and IP beats sudden spikes.
- Content and list quality - spammy phrasing, bad HTML, link reputation, and sending to dead addresses all hurt.
- One-click unsubscribe - a working List-Unsubscribe is now a placement factor for bulk mail.
What a diagnostic can and can't prove
This is the honest part. Our email diagnostic - and every tool like it - tests deliverability factors. It sends one message to a capture address and inspects authentication, DNS, transport and reputation signals. That's hugely useful: almost every "my mail goes to spam" problem starts as a deliverability fault (a broken SPF record, a missing DKIM signature, a blocklisted IP), and those are exactly what it catches.
What it cannot do is tell you which folder Gmail will choose for your next newsletter. No single-message test can, because placement depends on your reputation with that specific provider and on how their users have engaged with you over weeks. Be sceptical of any tool that claims a definitive "inbox placement score" from one send - real seed-list placement testing means sending to dozens of monitored mailboxes across providers, and even that is a snapshot, not a guarantee.
The right mental model: a clean diagnostic removes every reason to be rejected or junked. It clears the path. Walking it - earning inbox placement - is the ongoing work of sending wanted mail to people who engage with it.
JoltMx's Test Email tool proves the deliverability half directly: send to any address and see exactly what the destination server did - the SMTP reply, the negotiated TLS, and the full dialog. Acceptance is what it can prove; which folder the message lands in, it can't.
How JoltMx fits in
JoltMx is a routing and forwarding platform, so the deliverability fundamentals are our job: forwarded mail is re-signed and SRS-rewritten so it stays authenticated, connections use TLS, and every inbound message records its SPF / DKIM / DMARC results so you can see exactly how the internet judged it. The policy disposition check even previews how a strict receiver would treat a given message.
Placement then comes down to you sending mail people want. Start by making sure nothing mechanical is holding you back - run the diagnostic and clear every Warning and Critical first.
Related reading
Browse every diagnostic check · SPF, DKIM & DMARC explained · How disposition is decided