diff --git a/app/Mail/Concerns/SendsFromMailbox.php b/app/Mail/Concerns/SendsFromMailbox.php
new file mode 100644
index 0000000..c06bf9e
--- /dev/null
+++ b/app/Mail/Concerns/SendsFromMailbox.php
@@ -0,0 +1,37 @@
+<?php
+
+namespace App\Mail\Concerns;
+
+use App\Services\Mail\MailboxResolver;
+use Illuminate\Mail\Mailables\Address;
+use Illuminate\Mail\Mailables\Envelope;
+
+/**
+ * From and Reply-To, taken from the mailbox behind a purpose.
+ *
+ * Reply-To is the whole reason sending alone is enough: a customer answering a
+ * support reply lands in the support mailbox, read in an ordinary mail client,
+ * so no IMAP is needed to close the loop.
+ *
+ * Except on a no-reply mailbox. A "no-reply" address you can reply to is a lie
+ * in the sender, and the one place the promise is made is the address itself.
+ */
+trait SendsFromMailbox
+{
+    protected function mailboxEnvelope(string $purpose, string $subject): Envelope
+    {
+        $box = app(MailboxResolver::class)->for($purpose);
+
+        if ($box === null) {
+            // No mailbox configured yet — fall back to the framework default so
+            // an installation mid-setup still sends rather than crashing.
+            return new Envelope(subject: $subject);
+        }
+
+        return new Envelope(
+            from: new Address($box->address, $box->display_name ?: null),
+            replyTo: $box->no_reply ? [] : [new Address($box->address, $box->display_name ?: null)],
+            subject: $subject,
+        );
+    }
+}
diff --git a/app/Mail/MaintenanceAnnouncementMail.php b/app/Mail/MaintenanceAnnouncementMail.php
index ef9771c..5a69eda 100644
--- a/app/Mail/MaintenanceAnnouncementMail.php
+++ b/app/Mail/MaintenanceAnnouncementMail.php
@@ -2,8 +2,10 @@
 
 namespace App\Mail;
 
+use App\Mail\Concerns\SendsFromMailbox;
 use App\Models\Customer;
 use App\Models\MaintenanceWindow;
+use App\Services\Mail\MailPurpose;
 use Illuminate\Bus\Queueable;
 use Illuminate\Contracts\Queue\ShouldQueue;
 use Illuminate\Mail\Mailable;
@@ -14,7 +16,7 @@ use Illuminate\Queue\SerializesModels;
 
 class MaintenanceAnnouncementMail extends Mailable implements ShouldQueue
 {
-    use Queueable, SerializesModels;
+    use Queueable, SendsFromMailbox, SerializesModels;
 
     /** The ledger row this mail confirms once actually delivered. */
     public ?int $notificationId = null;
@@ -22,7 +24,11 @@ class MaintenanceAnnouncementMail extends Mailable implements ShouldQueue
     public function __construct(
         public MaintenanceWindow $window,
         public Customer $customer,
-    ) {}
+    ) {
+        // Names the mailer, which is all that is serialised into the queue —
+        // the credentials behind it are resolved when the worker sends.
+        $this->mailer('cp_'.MailPurpose::MAINTENANCE);
+    }
 
     public function headers(): Headers
     {
@@ -31,7 +37,10 @@ class MaintenanceAnnouncementMail extends Mailable implements ShouldQueue
 
     public function envelope(): Envelope
     {
-        return new Envelope(subject: __('maintenance.mail_subject', ['title' => $this->window->title]));
+        return $this->mailboxEnvelope(
+            MailPurpose::MAINTENANCE,
+            __('maintenance.mail_subject', ['title' => $this->window->title]),
+        );
     }
 
     public function content(): Content
diff --git a/app/Mail/MaintenanceCancelledMail.php b/app/Mail/MaintenanceCancelledMail.php
index 52293c4..e5a43a6 100644
--- a/app/Mail/MaintenanceCancelledMail.php
+++ b/app/Mail/MaintenanceCancelledMail.php
@@ -2,8 +2,10 @@
 
 namespace App\Mail;
 
+use App\Mail\Concerns\SendsFromMailbox;
 use App\Models\Customer;
 use App\Models\MaintenanceWindow;
+use App\Services\Mail\MailPurpose;
 use Illuminate\Bus\Queueable;
 use Illuminate\Contracts\Queue\ShouldQueue;
 use Illuminate\Mail\Mailable;
@@ -14,7 +16,7 @@ use Illuminate\Queue\SerializesModels;
 
 class MaintenanceCancelledMail extends Mailable implements ShouldQueue
 {
-    use Queueable, SerializesModels;
+    use Queueable, SendsFromMailbox, SerializesModels;
 
     /** The ledger row this mail confirms once actually delivered. */
     public ?int $notificationId = null;
@@ -22,7 +24,9 @@ class MaintenanceCancelledMail extends Mailable implements ShouldQueue
     public function __construct(
         public MaintenanceWindow $window,
         public Customer $customer,
-    ) {}
+    ) {
+        $this->mailer('cp_'.MailPurpose::MAINTENANCE);
+    }
 
     public function headers(): Headers
     {
@@ -31,7 +35,10 @@ class MaintenanceCancelledMail extends Mailable implements ShouldQueue
 
     public function envelope(): Envelope
     {
-        return new Envelope(subject: __('maintenance.mail_cancel_subject', ['title' => $this->window->title]));
+        return $this->mailboxEnvelope(
+            MailPurpose::MAINTENANCE,
+            __('maintenance.mail_cancel_subject', ['title' => $this->window->title]),
+        );
     }
 
     public function content(): Content
diff --git a/app/Notifications/CloudReady.php b/app/Notifications/CloudReady.php
index bd1273d..8d02112 100644
--- a/app/Notifications/CloudReady.php
+++ b/app/Notifications/CloudReady.php
@@ -3,6 +3,8 @@
 namespace App\Notifications;
 
 use App\Models\Instance;
+use App\Services\Mail\MailboxResolver;
+use App\Services\Mail\MailPurpose;
 use Illuminate\Bus\Queueable;
 use Illuminate\Notifications\Messages\MailMessage;
 use Illuminate\Notifications\Notification;
@@ -38,7 +40,20 @@ class CloudReady extends Notification
     {
         $url = 'https://'.$this->instance->subdomain.'.'.config('provisioning.dns.zone');
 
-        return (new MailMessage)
+        $box = app(MailboxResolver::class)
+            ->for(MailPurpose::PROVISIONING);
+
+        $message = (new MailMessage)->mailer('cp_'.MailPurpose::PROVISIONING);
+
+        if ($box !== null) {
+            $message->from($box->address, $box->display_name ?: null);
+
+            if (! $box->no_reply) {
+                $message->replyTo($box->address, $box->display_name ?: null);
+            }
+        }
+
+        return $message
             ->subject(__('provisioning.mail.ready_subject'))
             ->greeting(__('provisioning.mail.ready_greeting'))
             ->line(__('provisioning.mail.ready_line'))
diff --git a/tests/Feature/Mail/SenderAddressTest.php b/tests/Feature/Mail/SenderAddressTest.php
new file mode 100644
index 0000000..3bc1153
--- /dev/null
+++ b/tests/Feature/Mail/SenderAddressTest.php
@@ -0,0 +1,139 @@
+<?php
+
+use App\Mail\MaintenanceAnnouncementMail;
+use App\Mail\MaintenanceCancelledMail;
+use App\Models\Customer;
+use App\Models\Instance;
+use App\Models\Mailbox;
+use App\Models\MaintenanceWindow;
+use App\Notifications\CloudReady;
+use App\Services\Mail\MailPurpose;
+use App\Support\Settings;
+use Illuminate\Support\Facades\Crypt;
+
+beforeEach(function () {
+    config()->set('admin_access.secrets_key', 'base64:'.base64_encode(random_bytes(32)));
+});
+
+it('sends from the mailbox its purpose points at', function () {
+    Mailbox::factory()->create([
+        'key' => 'no-reply',
+        'address' => 'no-reply@clupilot.com',
+        'display_name' => 'CluPilot',
+        'no_reply' => true,
+    ]);
+    Settings::set(MailPurpose::settingKey(MailPurpose::MAINTENANCE), 'no-reply');
+
+    $mail = new MaintenanceAnnouncementMail(
+        MaintenanceWindow::factory()->create(),
+        Customer::factory()->create(),
+    );
+
+    $envelope = $mail->envelope();
+
+    expect($envelope->from->address)->toBe('no-reply@clupilot.com')
+        ->and($envelope->from->name)->toBe('CluPilot');
+});
+
+it('omits Reply-To on a no-reply mailbox, because that is what the name promises', function () {
+    Mailbox::factory()->create(['key' => 'no-reply', 'address' => 'no-reply@clupilot.com', 'no_reply' => true]);
+    Settings::set(MailPurpose::settingKey(MailPurpose::MAINTENANCE), 'no-reply');
+
+    $envelope = (new MaintenanceAnnouncementMail(
+        MaintenanceWindow::factory()->create(),
+        Customer::factory()->create(),
+    ))->envelope();
+
+    expect($envelope->replyTo)->toBeEmpty();
+});
+
+it('sets Reply-To on an answerable mailbox, so a customer reply reaches a human', function () {
+    Mailbox::factory()->create(['key' => 'support', 'address' => 'support@clupilot.com', 'no_reply' => false]);
+    Settings::set(MailPurpose::settingKey(MailPurpose::MAINTENANCE), 'support');
+
+    $envelope = (new MaintenanceAnnouncementMail(
+        MaintenanceWindow::factory()->create(),
+        Customer::factory()->create(),
+    ))->envelope();
+
+    expect($envelope->replyTo[0]->address)->toBe('support@clupilot.com');
+});
+
+it('names the purpose mailer so the queue worker picks the right transport', function () {
+    $mail = new MaintenanceAnnouncementMail(
+        MaintenanceWindow::factory()->create(),
+        Customer::factory()->create(),
+    );
+
+    expect($mail->mailer)->toBe('cp_maintenance');
+});
+
+it('gives the cancellation mail the same sender as the announcement', function () {
+    Mailbox::factory()->create(['key' => 'no-reply', 'address' => 'no-reply@clupilot.com', 'no_reply' => true]);
+    Settings::set(MailPurpose::settingKey(MailPurpose::MAINTENANCE), 'no-reply');
+
+    $mail = new MaintenanceCancelledMail(
+        MaintenanceWindow::factory()->create(),
+        Customer::factory()->create(),
+    );
+
+    expect($mail->envelope()->from->address)->toBe('no-reply@clupilot.com')
+        ->and($mail->mailer)->toBe('cp_maintenance');
+});
+
+it('falls back to the framework default envelope when no mailbox is configured for the purpose', function () {
+    // Neither a purpose mapping nor a system fallback exists anywhere in
+    // Settings — MailboxResolver::for() returns null. An installation
+    // mid-setup must still hand back a usable Envelope (subject intact)
+    // rather than dereferencing a null mailbox.
+    $window = MaintenanceWindow::factory()->create();
+
+    $envelope = (new MaintenanceAnnouncementMail($window, Customer::factory()->create()))->envelope();
+
+    expect($envelope->from)->toBeNull()
+        ->and($envelope->replyTo)->toBeEmpty()
+        ->and($envelope->subject)->toBe(__('maintenance.mail_subject', ['title' => $window->title]));
+});
+
+it('sends the provisioning notification from the provisioning mailbox', function () {
+    Mailbox::factory()->create([
+        'key' => 'no-reply',
+        'address' => 'no-reply@clupilot.com',
+        'display_name' => 'CluPilot',
+        'no_reply' => true,
+    ]);
+    Settings::set(MailPurpose::settingKey(MailPurpose::PROVISIONING), 'no-reply');
+
+    $notification = new CloudReady(
+        Instance::factory()->create(),
+        'admin',
+        Crypt::encryptString('geheim'),
+    );
+
+    $message = $notification->toMail(new stdClass);
+
+    expect($message->from[0])->toBe('no-reply@clupilot.com')
+        ->and($message->mailer)->toBe('cp_provisioning')
+        // no_reply is set, so no Reply-To — the same promise as everywhere else.
+        ->and($message->replyTo)->toBeEmpty();
+});
+
+it('sets Reply-To on the provisioning notification when its mailbox allows replies', function () {
+    // The mirror image of the no-reply case above: a support-style mailbox
+    // behind PROVISIONING must still get a Reply-To, the same as maintenance
+    // does. Without this, CloudReady's `if (! $box->no_reply)` branch is only
+    // ever exercised by the no_reply=true side and a deleted replyTo() call
+    // would go unnoticed.
+    Mailbox::factory()->create(['key' => 'support', 'address' => 'support@clupilot.com', 'no_reply' => false]);
+    Settings::set(MailPurpose::settingKey(MailPurpose::PROVISIONING), 'support');
+
+    $notification = new CloudReady(
+        Instance::factory()->create(),
+        'admin',
+        Crypt::encryptString('geheim'),
+    );
+
+    $message = $notification->toMail(new stdClass);
+
+    expect($message->replyTo[0][0])->toBe('support@clupilot.com');
+});