design: help, an allow entry by sender address trusts a claimed address

From the security review of 2026-10-12: the allow list matches the
envelope sender, which nobody authenticates. Help's Filter lists topic
says so and points to client addresses and networks.

check.py: 32 screens, 0 violations.

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

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

@@ -135,7 +135,7 @@
           <div class="sp-help-topic" id="recipients"><h3>Valid recipients</h3><p>Choose whom this domain accepts. Listed addresses only: the relay accepts exactly the addresses you list, one per line or comma-separated, and refuses any other while the sender is still connected, so it never has to send a bounce for them. Any recipient: everything at the domain is accepted and passed on, and an address the upstream then rejects comes back as a bounce from this server to a sender who is often forged — backscatter. Prefer a list, and keep it in step with the mailboxes upstream.</p></div>
           <div class="sp-help-topic" id="filter"><h3>Spam filter</h3><p>The spam filter belongs to the server, not to a domain. The server's administrator attaches it in the server's <code>.env</code>, and from then on every inbound domain is screened by it before mail is handed on; the box shows on or off and has nothing to switch. Off means mail goes to the upstream unfiltered. While the filter is down, mail is either accepted unfiltered (the default) or deferred, so the sending server tries again later, as the server's setting says; the box states which.</p></div>
           <div class="sp-help-topic" id="inbound-log"><h3>Inbound log</h3><p>One row per recipient of a message offered on port 25 for an inbound domain, with what was decided: <span class="tag is-success is-light">accept</span> — handed on to the upstream; <span class="tag is-danger is-light">reject</span> — refused for good; <span class="tag is-warning is-light">tempfail</span> — the sender was asked to come back later; <span class="tag is-primary is-light">quarantine</span> — held by the filter. <em>Why</em> names who decided. <code>rspamd</code> is the spam filter, with its action, the score against the reject threshold and the heaviest symbols; <code>postfix</code> is the relay's own rule — an unknown recipient, a sender domain that does not exist — with its reply; <code>selfpost</code> means nobody judged the message: it was relayed with no filter attached. Accept says what this server did, not what the upstream did with the message afterwards.<br><br>Accepted mail is recorded as it passes; refused mail is read from <code>mail.log</code>, so its row has no subject, and a message refused after its text was sent is one row however many recipients it had. A refusal to relay for a domain that is not an inbound one is every scanner on the internet and is not recorded. Rows are kept for the number of days set in Settings, and never more than 10 000.</p></div>
-          <div class="sp-help-topic" id="filter-lists"><h3>Filter lists</h3><p>Two lists for the whole server that correct the spam filter by hand. An entry is a sender address, a sender domain — that domain, not its subdomains — or a client address or network in CIDR form. A sender on the Deny list is refused outright. A sender on the Allow list is given a weight no spam score outweighs, so the filter lets it through. When entries of both lists match one message, <strong>Deny wins</strong>.<br><br>SelfPost does not apply the lists itself: it writes them as files under <code>/data/antispam/</code>, and rspamd rereads a file within seconds of a change. With the spam filter off the lists are kept and can be edited, but nothing reads them. The sender matched is the envelope sender — the one in the log — not the From line a mail program shows. Matched counts the messages in the Inbound log that the entry decided, so it reaches back as far as the log does; never means not once in that time, and such an entry is one to consider removing.</p></div>
+          <div class="sp-help-topic" id="filter-lists"><h3>Filter lists</h3><p>Two lists for the whole server that correct the spam filter by hand. An entry is a sender address, a sender domain — that domain, not its subdomains — or a client address or network in CIDR form. A sender on the Deny list is refused outright. A sender on the Allow list is given a weight no spam score outweighs, so the filter lets it through. The sender's address is whatever the sending server says it is - anyone can claim to be a sender you allow - so allow a client address or network where you can, and a sender address only for mail you would rather receive forged than lose. When entries of both lists match one message, <strong>Deny wins</strong>.<br><br>SelfPost does not apply the lists itself: it writes them as files under <code>/data/antispam/</code>, and rspamd rereads a file within seconds of a change. With the spam filter off the lists are kept and can be edited, but nothing reads them. The sender matched is the envelope sender — the one in the log — not the From line a mail program shows. Matched counts the messages in the Inbound log that the entry decided, so it reaches back as far as the log does; never means not once in that time, and such an entry is one to consider removing.</p></div>
         </div>
         <div class="box">
           <div class="sp-box-head"><span class="sp-no">04</span><h2>Server</h2></div>

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

@@ -69,7 +69,7 @@
           <div class="sp-help-topic" id="recipients"><h3>Valid recipients</h3><p>Choose whom this domain accepts. Listed addresses only: the relay accepts exactly the addresses you list, one per line or comma-separated, and refuses any other while the sender is still connected, so it never has to send a bounce for them. Any recipient: everything at the domain is accepted and passed on, and an address the upstream then rejects comes back as a bounce from this server to a sender who is often forged — backscatter. Prefer a list, and keep it in step with the mailboxes upstream.</p></div>
           <div class="sp-help-topic" id="filter"><h3>Spam filter</h3><p>The spam filter belongs to the server, not to a domain. The server's administrator attaches it in the server's <code>.env</code>, and from then on every inbound domain is screened by it before mail is handed on; the box shows on or off and has nothing to switch. Off means mail goes to the upstream unfiltered. While the filter is down, mail is either accepted unfiltered (the default) or deferred, so the sending server tries again later, as the server's setting says; the box states which.</p></div>
           <div class="sp-help-topic" id="inbound-log"><h3>Inbound log</h3><p>One row per recipient of a message offered on port 25 for an inbound domain, with what was decided: <span class="tag is-success is-light">accept</span> — handed on to the upstream; <span class="tag is-danger is-light">reject</span> — refused for good; <span class="tag is-warning is-light">tempfail</span> — the sender was asked to come back later; <span class="tag is-primary is-light">quarantine</span> — held by the filter. <em>Why</em> names who decided. <code>rspamd</code> is the spam filter, with its action, the score against the reject threshold and the heaviest symbols; <code>postfix</code> is the relay's own rule — an unknown recipient, a sender domain that does not exist — with its reply; <code>selfpost</code> means nobody judged the message: it was relayed with no filter attached. Accept says what this server did, not what the upstream did with the message afterwards.<br><br>Accepted mail is recorded as it passes; refused mail is read from <code>mail.log</code>, so its row has no subject, and a message refused after its text was sent is one row however many recipients it had. A refusal to relay for a domain that is not an inbound one is every scanner on the internet and is not recorded. Rows are kept for the number of days set in Settings, and never more than 10 000.</p></div>
-          <div class="sp-help-topic" id="filter-lists"><h3>Filter lists</h3><p>Two lists for the whole server that correct the spam filter by hand. An entry is a sender address, a sender domain — that domain, not its subdomains — or a client address or network in CIDR form. A sender on the Deny list is refused outright. A sender on the Allow list is given a weight no spam score outweighs, so the filter lets it through. When entries of both lists match one message, <strong>Deny wins</strong>.<br><br>SelfPost does not apply the lists itself: it writes them as files under <code>/data/antispam/</code>, and rspamd rereads a file within seconds of a change. With the spam filter off the lists are kept and can be edited, but nothing reads them. The sender matched is the envelope sender — the one in the log — not the From line a mail program shows. Matched counts the messages in the Inbound log that the entry decided, so it reaches back as far as the log does; never means not once in that time, and such an entry is one to consider removing.</p></div>
+          <div class="sp-help-topic" id="filter-lists"><h3>Filter lists</h3><p>Two lists for the whole server that correct the spam filter by hand. An entry is a sender address, a sender domain — that domain, not its subdomains — or a client address or network in CIDR form. A sender on the Deny list is refused outright. A sender on the Allow list is given a weight no spam score outweighs, so the filter lets it through. The sender's address is whatever the sending server says it is - anyone can claim to be a sender you allow - so allow a client address or network where you can, and a sender address only for mail you would rather receive forged than lose. When entries of both lists match one message, <strong>Deny wins</strong>.<br><br>SelfPost does not apply the lists itself: it writes them as files under <code>/data/antispam/</code>, and rspamd rereads a file within seconds of a change. With the spam filter off the lists are kept and can be edited, but nothing reads them. The sender matched is the envelope sender — the one in the log — not the From line a mail program shows. Matched counts the messages in the Inbound log that the entry decided, so it reaches back as far as the log does; never means not once in that time, and such an entry is one to consider removing.</p></div>
         </div>
         <div class="box">
           <div class="sp-box-head"><span class="sp-no">04</span><h2>Server</h2></div>