Silence has a cause, and almost always the product already knows which one and has written it on the screen. Work down this list rather than starting with “email is broken” — the delivery explanations are at the bottom because they are the least common.
1. The thread is paused
The most easily missed, because nothing looks wrong. The banner is explicit:
AI is paused on this thread. Inbound replies will not trigger an automatic AI response until someone hands the thread back to the AI.
If a reply was actually generated while paused, it is shown and labelled rather than silently dropped:
Suppressed: the AI would have sent this reply, but the thread is paused. No email was delivered.
The reply-mode control reads Paused (resume to …) and names what it will return to. Somebody paused this on purpose — usually because a human took the conversation over.
2. It wrote a draft and nobody approved it
If the mailbox is in Drafts mode, a written reply is the expected outcome and sending is a human action. Check Pending drafts (3) and the Drafts filter. A thread showing AI draft — pending review is not stuck; it is waiting for you. More on that flow.
3. The mode is Human only
Shown as You · No AI, with “No AI runs on this thread.” under the control. No AI ran, by design. This is either the channel default or an override on this one thread.
4. No agent is assigned
A mailbox with no agent has nothing to write with, and the message says so:
No agent is assigned to this mailbox yet, so nothing is writing replies.
This is a misconfiguration rather than a setting, and it is worth fixing rather than working around — bind an agent to the channel.
5. The sender was a no-reply address
Deliberate, and stated on the message itself:
No reply drafted · This came from a no-reply address, so a reply would not reach anyone.
Mail from no-reply@, donotreply@ and their variants is shown to you and never
answered. A reply would bounce, and the thread would then read as unanswered
forever.
6. It never reached us at all
Some mail is dropped before the AI sees it, because answering it would start a loop. Anything that self-identifies as machine-generated:
Auto-Submittedset to anything other thanno(RFC 3834)Precedence: bulk,auto_reply, orlist- Mailing-list mail carrying
List-IdorList-Unsubscribe - Bounces and postmaster notifications
These are dropped rather than shown. If you expected a reply to a newsletter or an automated notification, this is why there is no thread at all.
7. The channel is disconnected
Unmissable once you look, and easy to miss if you are looking at an old thread:
Channel disconnected. Past messages remain visible above, but the AI can no longer reply and you can’t send from here. Re-connect the mailbox in Settings → Channels to resume.
A revoked OAuth grant, a changed password, or an administrator removing the permission the connection borrows will all land here.
8. It looks unanswered, and a human already answered it
Not a fault — a counting limitation, and worth understanding because it makes threads look worse than they are.
The platform credits replies that went out through it. A colleague who answers from Gmail or Outlook directly has genuinely dealt with the customer, but that reply is not recorded as an answer here, so the thread can still appear to be waiting.
On Gmail we never receive their reply at all — the watch is armed on the inbox. On Outlook we do receive it, and still do not mark the thread answered.
What this page is not about
Everything above is a rules problem: something decided not to reply, and said so. If a reply was genuinely sent from here and the recipient never received it, that is a delivery problem — SPF, DKIM, your domain’s reputation, the recipient’s spam filter — and those live with your mail provider and your DNS, not in this product. We do not manage or monitor them, and a guide claiming otherwise would be selling you something that is not here.
The way to tell them apart: if the thread shows a sent reply, the rules worked and the question is delivery. If it shows nothing, or shows a draft, or shows one of the notices above, the answer is somewhere on this page.