3 files changed, 137 insertions, 0 deletions
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index d4f1cb7..7cec9b3 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -10,6 +10,7 @@ add_library(qtmaildir_lib STATIC
     cardlayout.cpp
     avatar.cpp
     busyindicator.cpp
+    businesssenders.cpp
     marks.cpp
     carddelegate.cpp
     notmuchworker.cpp
diff --git a/src/businesssenders.cpp b/src/businesssenders.cpp
new file mode 100644
index 0000000..13a9374
--- /dev/null
+++ b/src/businesssenders.cpp
@@ -0,0 +1,78 @@
+/*
+ * qtmaildir - a Qt6 mail client for notmuch-indexed Maildirs
+ * Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "businesssenders.h"
+
+#include <QDir>
+#include <QFile>
+#include <QStandardPaths>
+#include <QTextStream>
+
+namespace BusinessSenders {
+
+List parse(const QString &contents)
+{
+    List list;
+    const QStringList lines = contents.split(QLatin1Char('\n'));
+    for (const QString &raw : lines) {
+        const QString line = raw.trimmed();
+        // A commented entry is the reject gesture: it stays in the file so it
+        // is never proposed again, and it is not applied.
+        if (line.isEmpty() || line.startsWith(QLatin1Char('#')))
+            continue;
+
+        const QString entry = line.toLower();
+        if (entry.startsWith(QLatin1Char('@')))
+            list.domains.insert(entry.mid(1));
+        else
+            list.addresses.insert(entry);
+    }
+    return list;
+}
+
+List load(const QString &path)
+{
+    QFile file(path);
+    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
+        return List();
+    return parse(QString::fromUtf8(file.readAll()));
+}
+
+bool contains(const List &list, const QString &address)
+{
+    const QString lowered = address.trimmed().toLower();
+    if (lowered.isEmpty())
+        return false;
+    if (list.addresses.contains(lowered))
+        return true;
+
+    const int at = lowered.indexOf(QLatin1Char('@'));
+    if (at < 0)
+        return false;
+    return list.domains.contains(lowered.mid(at + 1));
+}
+
+QString defaultPath()
+{
+    const QString base = QStandardPaths::writableLocation(
+        QStandardPaths::GenericConfigLocation);
+    return QDir(base).filePath(
+        QStringLiteral("qtmaildir/business-senders"));
+}
+
+} // namespace BusinessSenders
diff --git a/src/businesssenders.h b/src/businesssenders.h
new file mode 100644
index 0000000..0689453
--- /dev/null
+++ b/src/businesssenders.h
@@ -0,0 +1,58 @@
+/*
+ * qtmaildir - a Qt6 mail client for notmuch-indexed Maildirs
+ * Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#pragma once
+
+#include <QSet>
+#include <QString>
+#include <QStringList>
+
+/// The list of senders that read as businesses rather than people.
+///
+/// `~/.config/qtmaildir/business-senders`, plain text, one entry per line,
+/// `#` comments, blank lines ignored. Deliberately NOT in qtmaildir.conf and
+/// deliberately not INI: the user's stated workflow is grep-and-edit, QSettings
+/// would fight a bare list, and the main config is already large.
+///
+/// An entry is an exact address (`noreply@cofidis.it`) or a whole domain
+/// (`@cofidis.it`). No globs: a pattern language is a rule the user cannot grep
+/// for literally, which defeats the file's purpose.
+namespace BusinessSenders
+{
+
+/// Parsed entries, lower-cased. Two sets rather than one list so a lookup is a
+/// hash probe per repaint rather than a walk.
+struct List
+{
+    QSet<QString> addresses;
+    QSet<QString> domains;   ///< Stored WITHOUT the leading '@'.
+};
+
+List parse(const QString &contents);
+
+/// Reads `path`. A missing or unreadable file yields an empty list rather than
+/// an error: the feature is cosmetic and must never block startup.
+List load(const QString &path);
+
+bool contains(const List &list, const QString &address);
+
+/// `~/.config/qtmaildir/business-senders`, built from
+/// QStandardPaths::GenericConfigLocation.
+QString defaultPath();
+
+} // namespace BusinessSenders