design: help - the sender check holds Sender: too

The owner's decision (2026-10-16, security review of panel-dkim-signing,
F1): a Sender: line, shown beside From: as "on behalf of", is held to the
same rule when a message has one. The topic says how a system that writes
for people outside the server's domains does it instead (its own From:, the
person in Reply-To:), and the Outbound log topic names Sender: among the
refusals.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/assets/panel-redesign/panel/help.html

@@ -125,9 +125,9 @@
           <div class="sp-box-head"><span class="sp-no">02</span><h2>Outbound</h2></div>
           <div class="sp-help-topic" id="dns"><h3>DNS records</h3><p>DKIM proves the message was signed by this relay, SPF lists the addresses allowed to send for the domain, DMARC tells receivers what to do when both fail and where to report. Publish all three exactly as shown; merge SPF into an existing record rather than adding a second one. A domain's status is the worst of its three records, and results are cached for a few minutes, so use Re-check DNS after publishing. The SPF check is shallow: it looks for this server's address in the record itself and does not follow <code>include:</code> or <code>redirect=</code>, so a record that relies on them is reported as a warning, not a failure. <code>p=none</code> does not affect delivery; tighten to <code>quarantine</code>, then <code>reject</code>, once the reports look clean. A domain's report address is set in its Domain settings.</p></div>
           <div class="sp-help-topic" id="apps"><h3>Applications</h3><p>An application is one SASL login, unique across all domains. It may send as any address of its domain or only as listed addresses, and, with a list of client IPs set, only from those addresses. The password is shown once at creation or regeneration and is not stored in readable form.</p></div>
-          <div class="sp-help-topic" id="sender-check"><h3>Sender check</h3><p>An application sends only as itself, and that holds for both senders a message has. The envelope sender is held against the login by Postfix. The <code>From:</code> line, the one a mail program shows and the one DMARC holds the DKIM signature to, is held against it by the panel, under the same rule: an application set to any address of its domain may write any address of that domain, and one with a list of addresses only those. A message with any other <code>From:</code> - another of your domains, the server's own name, an address somewhere else, or none at all - is refused for good with <code>550 5.7.1</code>. The line must hold one address, read as a mail program reads it: what a display name around it says is not judged, and a line holding more than one address is refused. It is a rejected row of the Outbound log, and its page says which address was refused. This is what keeps one application from sending, under this server's signature, as another domain or another application.<br><br>The check is strict. While the panel does not answer, Postfix does not accept mail unchecked: it replies with a temporary error and the application sends again later. Server › Health counts what that costs: for how long the panel did not answer while Postfix itself was running; how many connections Postfix turned away because of it - it refuses from the connection on, before a message is offered, so a client that tries three times is three and a monitor that only connects is one; and how many messages were refused with a temporary error in the middle, when the panel stopped answering after a message had begun. A time marked ≈ includes a start at which supervisord could not say since when Postfix was running: the time since the panel's last sign of life is counted, which may be more than Postfix was up. The card warns when a connection was turned away or a message refused in the last 24 hours. If the numbers stay at nothing, the check is where it should be; if they do not, it belongs in a process of its own.</p></div>
+          <div class="sp-help-topic" id="sender-check"><h3>Sender check</h3><p>An application sends only as itself, and that holds for every sender a message names. The envelope sender is held against the login by Postfix. The <code>From:</code> line, the one a mail program shows and the one DMARC holds the DKIM signature to, is held against it by the panel, under the same rule: an application set to any address of its domain may write any address of that domain, and one with a list of addresses only those. A message with any other <code>From:</code> - another of your domains, the server's own name, an address somewhere else, or none at all - is refused for good with <code>550 5.7.1</code>. The line must hold one address, read as a mail program reads it: what a display name around it says is not judged, and a line holding more than one address is refused. A <code>Sender:</code> line, which a mail program shows beside <code>From:</code> as "on behalf of", is held to the same rule when the message has one. A system that writes for people outside your domains writes its own address in <code>From:</code> with the person's name, and the person's address in <code>Reply-To:</code>: their domain in <code>From:</code> would fail DMARC at the receiver anyway. It is a rejected row of the Outbound log, and its page says which address was refused. This is what keeps one application from sending, under this server's signature, as another domain or another application.<br><br>The check is strict. While the panel does not answer, Postfix does not accept mail unchecked: it replies with a temporary error and the application sends again later. Server › Health counts what that costs: for how long the panel did not answer while Postfix itself was running; how many connections Postfix turned away because of it - it refuses from the connection on, before a message is offered, so a client that tries three times is three and a monitor that only connects is one; and how many messages were refused with a temporary error in the middle, when the panel stopped answering after a message had begun. A time marked ≈ includes a start at which supervisord could not say since when Postfix was running: the time since the panel's last sign of life is counted, which may be more than Postfix was up. The card warns when a connection was turned away or a message refused in the last 24 hours. If the numbers stay at nothing, the check is where it should be; if they do not, it belongs in a process of its own.</p></div>
           <div class="sp-help-topic" id="limits"><h3>Rate limits</h3><p>Level 1 is a per-IP ceiling set in <code>.env</code>. Level 2 is optional, per domain and per application, entered by hand or computed from the last 30 days of sending, and can never exceed level 1. An application's own limit replaces its domain's.</p></div>
-          <div class="sp-help-topic" id="log"><h3>Outbound log</h3><p>One row per message and recipient, with the status Postfix last reported: queued (accepted, nothing reported yet), sent (the receiving server took it; what the mailbox does next is not reported back), deferred (not taken yet, Postfix tries again), bounced (failed for good, or the queue lifetime ran out; or closed by the panel when Postfix no longer held the message and <code>mail.log</code> never said what became of it) and rejected (refused before queueing, so it never reached the queue: under a level-2 rate limit, from a client address the application does not allow, or for a <code>From:</code> line that is not the application's - the message's page says which). A message's page lists these steps and the lines Postfix wrote about it in <code>mail.log</code>, found by queue id - and for a message refused before it had one, Postfix's one line about the refusal. The lines are kept with the row: they stay on the page after that file has rotated, for as long as the row does. A message accepted before version 2.2.0 shows them only while they are still in the current file. Rows are deleted after the retention set in Server › Settings, 90 days by default, and their lines with them. A domain administrator sees only the rows of their own domains.</p></div>
+          <div class="sp-help-topic" id="log"><h3>Outbound log</h3><p>One row per message and recipient, with the status Postfix last reported: queued (accepted, nothing reported yet), sent (the receiving server took it; what the mailbox does next is not reported back), deferred (not taken yet, Postfix tries again), bounced (failed for good, or the queue lifetime ran out; or closed by the panel when Postfix no longer held the message and <code>mail.log</code> never said what became of it) and rejected (refused before queueing, so it never reached the queue: under a level-2 rate limit, from a client address the application does not allow, or for a <code>From:</code> or <code>Sender:</code> line that is not the application's - the message's page says which). A message's page lists these steps and the lines Postfix wrote about it in <code>mail.log</code>, found by queue id - and for a message refused before it had one, Postfix's one line about the refusal. The lines are kept with the row: they stay on the page after that file has rotated, for as long as the row does. A message accepted before version 2.2.0 shows them only while they are still in the current file. Rows are deleted after the retention set in Server › Settings, 90 days by default, and their lines with them. A domain administrator sees only the rows of their own domains.</p></div>
           <div class="sp-help-topic" id="queue"><h3>Queue and retries</h3><p>The page lists, as <code>postqueue -p</code> prints it, the messages Postfix has accepted and not yet delivered: mail being sent right now and mail deferred for a later attempt. Only the global role can open it, and it only shows; nothing here deletes or forces a message. A deferred message is tried again after the first retry delay, then at gaps that double up to a cap, until the receiving server takes it or the queue lifetime runs out and it bounces; there is no attempt counter, and the box on the page shows this server's values. A queue that keeps growing means a receiver is refusing or not answering: open the message from the Outbound log to read the reason Postfix logged.</p></div>
           <div class="sp-help-topic" id="dmarc"><h3>DMARC reports</h3><p>An aggregate report is the summary a receiving provider sends, usually daily, to the <code>rua=</code> address of your DMARC record: which servers sent mail as your domain and whether SPF or DKIM passed for it. A domain's report address is one of three choices, set in its Domain settings: no reports (the default for a new domain), the SelfPost hosted address (an address on this server whose reports are parsed and shown under DMARC reports; offered only while hosted reports are enabled on the server), or an address typed for the domain (an ordinary mailbox that receives the raw XML; a button fills in your own profile e-mail). When the typed address is on another domain than the one sending, that domain must publish a report-authorization record, or providers will not send; the domain's page shows it with the other DNS records and checks it. In the tables pass means SPF or DKIM passed and aligned, fail means neither did, and your own server shows as <em>this relay</em>. A fail from any other source is someone else sending as your domain — a forwarder, an application you forgot, or abuse — so do not tighten <code>p=</code> until that sender is fixed or removed. A domain administrator reads the reports of their own domains.</p></div>
         </div>

docs/assets/panel-redesign/panel/src/help.html

@@ -59,9 +59,9 @@
           <div class="sp-box-head"><span class="sp-no">02</span><h2>Outbound</h2></div>
           <div class="sp-help-topic" id="dns"><h3>DNS records</h3><p>DKIM proves the message was signed by this relay, SPF lists the addresses allowed to send for the domain, DMARC tells receivers what to do when both fail and where to report. Publish all three exactly as shown; merge SPF into an existing record rather than adding a second one. A domain's status is the worst of its three records, and results are cached for a few minutes, so use Re-check DNS after publishing. The SPF check is shallow: it looks for this server's address in the record itself and does not follow <code>include:</code> or <code>redirect=</code>, so a record that relies on them is reported as a warning, not a failure. <code>p=none</code> does not affect delivery; tighten to <code>quarantine</code>, then <code>reject</code>, once the reports look clean. A domain's report address is set in its Domain settings.</p></div>
           <div class="sp-help-topic" id="apps"><h3>Applications</h3><p>An application is one SASL login, unique across all domains. It may send as any address of its domain or only as listed addresses, and, with a list of client IPs set, only from those addresses. The password is shown once at creation or regeneration and is not stored in readable form.</p></div>
-          <div class="sp-help-topic" id="sender-check"><h3>Sender check</h3><p>An application sends only as itself, and that holds for both senders a message has. The envelope sender is held against the login by Postfix. The <code>From:</code> line, the one a mail program shows and the one DMARC holds the DKIM signature to, is held against it by the panel, under the same rule: an application set to any address of its domain may write any address of that domain, and one with a list of addresses only those. A message with any other <code>From:</code> - another of your domains, the server's own name, an address somewhere else, or none at all - is refused for good with <code>550 5.7.1</code>. The line must hold one address, read as a mail program reads it: what a display name around it says is not judged, and a line holding more than one address is refused. It is a rejected row of the Outbound log, and its page says which address was refused. This is what keeps one application from sending, under this server's signature, as another domain or another application.<br><br>The check is strict. While the panel does not answer, Postfix does not accept mail unchecked: it replies with a temporary error and the application sends again later. Server › Health counts what that costs: for how long the panel did not answer while Postfix itself was running; how many connections Postfix turned away because of it - it refuses from the connection on, before a message is offered, so a client that tries three times is three and a monitor that only connects is one; and how many messages were refused with a temporary error in the middle, when the panel stopped answering after a message had begun. A time marked ≈ includes a start at which supervisord could not say since when Postfix was running: the time since the panel's last sign of life is counted, which may be more than Postfix was up. The card warns when a connection was turned away or a message refused in the last 24 hours. If the numbers stay at nothing, the check is where it should be; if they do not, it belongs in a process of its own.</p></div>
+          <div class="sp-help-topic" id="sender-check"><h3>Sender check</h3><p>An application sends only as itself, and that holds for every sender a message names. The envelope sender is held against the login by Postfix. The <code>From:</code> line, the one a mail program shows and the one DMARC holds the DKIM signature to, is held against it by the panel, under the same rule: an application set to any address of its domain may write any address of that domain, and one with a list of addresses only those. A message with any other <code>From:</code> - another of your domains, the server's own name, an address somewhere else, or none at all - is refused for good with <code>550 5.7.1</code>. The line must hold one address, read as a mail program reads it: what a display name around it says is not judged, and a line holding more than one address is refused. A <code>Sender:</code> line, which a mail program shows beside <code>From:</code> as "on behalf of", is held to the same rule when the message has one. A system that writes for people outside your domains writes its own address in <code>From:</code> with the person's name, and the person's address in <code>Reply-To:</code>: their domain in <code>From:</code> would fail DMARC at the receiver anyway. It is a rejected row of the Outbound log, and its page says which address was refused. This is what keeps one application from sending, under this server's signature, as another domain or another application.<br><br>The check is strict. While the panel does not answer, Postfix does not accept mail unchecked: it replies with a temporary error and the application sends again later. Server › Health counts what that costs: for how long the panel did not answer while Postfix itself was running; how many connections Postfix turned away because of it - it refuses from the connection on, before a message is offered, so a client that tries three times is three and a monitor that only connects is one; and how many messages were refused with a temporary error in the middle, when the panel stopped answering after a message had begun. A time marked ≈ includes a start at which supervisord could not say since when Postfix was running: the time since the panel's last sign of life is counted, which may be more than Postfix was up. The card warns when a connection was turned away or a message refused in the last 24 hours. If the numbers stay at nothing, the check is where it should be; if they do not, it belongs in a process of its own.</p></div>
           <div class="sp-help-topic" id="limits"><h3>Rate limits</h3><p>Level 1 is a per-IP ceiling set in <code>.env</code>. Level 2 is optional, per domain and per application, entered by hand or computed from the last 30 days of sending, and can never exceed level 1. An application's own limit replaces its domain's.</p></div>
-          <div class="sp-help-topic" id="log"><h3>Outbound log</h3><p>One row per message and recipient, with the status Postfix last reported: queued (accepted, nothing reported yet), sent (the receiving server took it; what the mailbox does next is not reported back), deferred (not taken yet, Postfix tries again), bounced (failed for good, or the queue lifetime ran out; or closed by the panel when Postfix no longer held the message and <code>mail.log</code> never said what became of it) and rejected (refused before queueing, so it never reached the queue: under a level-2 rate limit, from a client address the application does not allow, or for a <code>From:</code> line that is not the application's - the message's page says which). A message's page lists these steps and the lines Postfix wrote about it in <code>mail.log</code>, found by queue id - and for a message refused before it had one, Postfix's one line about the refusal. The lines are kept with the row: they stay on the page after that file has rotated, for as long as the row does. A message accepted before version 2.2.0 shows them only while they are still in the current file. Rows are deleted after the retention set in Server › Settings, 90 days by default, and their lines with them. A domain administrator sees only the rows of their own domains.</p></div>
+          <div class="sp-help-topic" id="log"><h3>Outbound log</h3><p>One row per message and recipient, with the status Postfix last reported: queued (accepted, nothing reported yet), sent (the receiving server took it; what the mailbox does next is not reported back), deferred (not taken yet, Postfix tries again), bounced (failed for good, or the queue lifetime ran out; or closed by the panel when Postfix no longer held the message and <code>mail.log</code> never said what became of it) and rejected (refused before queueing, so it never reached the queue: under a level-2 rate limit, from a client address the application does not allow, or for a <code>From:</code> or <code>Sender:</code> line that is not the application's - the message's page says which). A message's page lists these steps and the lines Postfix wrote about it in <code>mail.log</code>, found by queue id - and for a message refused before it had one, Postfix's one line about the refusal. The lines are kept with the row: they stay on the page after that file has rotated, for as long as the row does. A message accepted before version 2.2.0 shows them only while they are still in the current file. Rows are deleted after the retention set in Server › Settings, 90 days by default, and their lines with them. A domain administrator sees only the rows of their own domains.</p></div>
           <div class="sp-help-topic" id="queue"><h3>Queue and retries</h3><p>The page lists, as <code>postqueue -p</code> prints it, the messages Postfix has accepted and not yet delivered: mail being sent right now and mail deferred for a later attempt. Only the global role can open it, and it only shows; nothing here deletes or forces a message. A deferred message is tried again after the first retry delay, then at gaps that double up to a cap, until the receiving server takes it or the queue lifetime runs out and it bounces; there is no attempt counter, and the box on the page shows this server's values. A queue that keeps growing means a receiver is refusing or not answering: open the message from the Outbound log to read the reason Postfix logged.</p></div>
           <div class="sp-help-topic" id="dmarc"><h3>DMARC reports</h3><p>An aggregate report is the summary a receiving provider sends, usually daily, to the <code>rua=</code> address of your DMARC record: which servers sent mail as your domain and whether SPF or DKIM passed for it. A domain's report address is one of three choices, set in its Domain settings: no reports (the default for a new domain), the SelfPost hosted address (an address on this server whose reports are parsed and shown under DMARC reports; offered only while hosted reports are enabled on the server), or an address typed for the domain (an ordinary mailbox that receives the raw XML; a button fills in your own profile e-mail). When the typed address is on another domain than the one sending, that domain must publish a report-authorization record, or providers will not send; the domain's page shows it with the other DNS records and checks it. In the tables pass means SPF or DKIM passed and aligned, fail means neither did, and your own server shows as <em>this relay</em>. A fail from any other source is someone else sending as your domain — a forwarder, an application you forgot, or abuse — so do not tighten <code>p=</code> until that sender is fixed or removed. A domain administrator reads the reports of their own domains.</p></div>
         </div>