add.go     |  47 +++++++++++++++++++++++++++++++++++++++++++++++
 db/help-en |  29 +++++++++++++++++++++++++++++
 db/help-ru |  29 +++++++++++++++++++++++++++++
 db/motd    |   5 +++++
 get.go     |  26 ++++++++++++++++++++++++++
 go.mod     |   8 ++++++++
 go.sum     |   4 ++++
 main.go    |  50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 new.go     | 107 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 notify.go  |  38 ++++++++++++++++++++++++++++++++++++++

diff --git a/add.go b/add.go
new file mode 100644
index 0000000000000000000000000000000000000000..5cd014a6be58fdd97a012b5562c3f394d51f6d75d757f61f2a7166dd206379ce
--- /dev/null
+++ b/add.go
@@ -0,0 +1,47 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"os"
+	"path"
+
+	"github.com/google/uuid"
+	"go.stargrave.org/recfile/v4"
+)
+
+func doAdd() error {
+	if len(Args) != 2 {
+		return errors.New("no id supplied")
+	}
+	id, err := uuid.Parse(Args[1])
+	if err != nil {
+		return err
+	}
+	body, err := msgRead()
+	if err != nil {
+		return err
+	}
+	fn := path.Join(DB, id.String())
+	fh, err := os.OpenFile(fn, os.O_WRONLY|os.O_APPEND, 0o666)
+	if err != nil {
+		return err
+	}
+	defer fh.Close()
+	bw := bufio.NewWriter(fh)
+	w := recfile.NewWriter(bw)
+	if err = metaWrite(w); err != nil {
+		return err
+	}
+	if _, err = w.WriteField("body", body); err != nil {
+		return err
+	}
+	if err = bw.Flush(); err != nil {
+		return err
+	}
+	if err = fh.Close(); err != nil {
+		return err
+	}
+	notify(id.String())
+	return nil
+}
diff --git a/db/help-en b/db/help-en
new file mode 100644
index 0000000000000000000000000000000000000000..2050dbf9778b9929e4b595e6069df06c8a8f9e95c61e8d47737c3b133ca5387e
--- /dev/null
+++ b/db/help-en
@@ -0,0 +1,29 @@
+To leave a message to operator, call the system with "new" command:
+
+    $ ssh -C msg@msg.stargrave.org new The subject line <<EOF
+    > Multiline
+    > message body
+    > I want to leave
+    > EOF
+    < cd6e391a-9eec-46be-9f39-84f6011944f5
+
+That cd6e391a-9eec-46be-9f39-84f6011944f5 is thread identifier.
+
+Now you can check if there is any reply left from the operator:
+
+    $ ssh -C msg@msg.stargrave.org get cd6e391a-9eec-46be-9f39-84f6011944f5
+    subj: The subject line for the thread
+
+    when: 2026-05-06 14:26:27+03:00
+    from: ::1 64254 22
+    body:
+    + Multiline
+    + message body
+    + I want to leave
+
+To add/reply another message to that thread:
+
+    $ ssh -C msg@msg.stargrave.org add cd6e391a-9eec-46be-9f39-84f6011944f5 <<EOF
+    > Reply to the existing thread.
+    > Add another message.
+    > EOF
diff --git a/db/help-ru b/db/help-ru
new file mode 100644
index 0000000000000000000000000000000000000000..f4348f4d9aa711d87801fbb205355717aea0f04f23aaf15aa5bf493d6c840699
--- /dev/null
+++ b/db/help-ru
@@ -0,0 +1,29 @@
+Чтобы оставить сообщение оператору, вызовите систему с "new" командой:
+
+    $ ssh -C msg@msg.stargrave.org new Это тема сообщения <<EOF
+    > Многострочное
+    > тело сообщения
+    > которое я хочу оставить
+    > EOF
+    < cd6e391a-9eec-46be-9f39-84f6011944f5
+
+Этот cd6e391a-9eec-46be-9f39-84f6011944f5 является идентификатором нити.
+
+Теперь вы можете проверить не оставил ли оператор ответа:
+
+    $ ssh -C msg@msg.stargrave.org get cd6e391a-9eec-46be-9f39-84f6011944f5
+    subj: Это тема сообщения
+
+    when: 2026-05-06 14:26:27+03:00
+    from: ::1 64254 22
+    body:
+    + Многострочное
+    + тело сообщения
+    + которое я хочу оставить
+
+Чтобы добавить/ответить другим сообщением в этой нити:
+
+    $ ssh -C msg@msg.stargrave.org add cd6e391a-9eec-46be-9f39-84f6011944f5 <<EOF
+    > Ответ в существующую нить.
+    > Добавить ещё одно сообщение.
+    > EOF
diff --git a/db/motd b/db/motd
new file mode 100644
index 0000000000000000000000000000000000000000..bfe82e7606225f78f884ccac222096db14bae36f94fb65ef54b8f019c0e1c767
--- /dev/null
+++ b/db/motd
@@ -0,0 +1,5 @@
+                  Welcome to simple messaging system!
+         Добро пожаловать в простую систему обмена сообщениями!
+--------------------------------------------------------------------------------
+To get help use: ssh msg@msg.stargrave.org get help-en
+Для получения справки используйте: ssh msg@msg.stargrave.org get help-ru
diff --git a/get.go b/get.go
new file mode 100644
index 0000000000000000000000000000000000000000..5c51aa3ea188a98cec8a261f8dd02d14b426bc3ebbf75ccad761fe8e35c1a3ec
--- /dev/null
+++ b/get.go
@@ -0,0 +1,26 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"os"
+	"path"
+	"regexp"
+)
+
+func doGet() error {
+	if len(Args) != 2 {
+		return errors.New("no id supplied")
+	}
+	re := regexp.MustCompile("^[a-zA-Z0-9-]+$")
+	if !re.MatchString(Args[1]) {
+		return errors.New("bad id supplied")
+	}
+	fh, err := os.Open(path.Join(DB, Args[1]))
+	if err != nil {
+		return err
+	}
+	_, err = io.Copy(os.Stdout, bufio.NewReader(fh))
+	return err
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000000000000000000000000000000000000..3d3181d024efd3addb13ab91012f7b388fac05d1c974a5cbf22aaf761049cda4
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,8 @@
+module go.stargrave.org/msshg
+
+go 1.26.2
+
+require (
+	github.com/google/uuid v1.6.0
+	go.stargrave.org/recfile/v4 v4.0.0
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000000000000000000000000000000000000..68c75d66df8dd5f2661f24eed59159a1a2d1fcaabe49d260b17c860050e9e8c3
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,4 @@
+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+go.stargrave.org/recfile/v4 v4.0.0 h1:v9kZnW/e64oPfOqArGMNZacuT57lDibd24xhEiBDQ/c=
+go.stargrave.org/recfile/v4 v4.0.0/go.mod h1:IGi8kMociIlDoR8iOssyUG/uix+wmsqvBuiDeQXsIuE=
diff --git a/main.go b/main.go
new file mode 100644
index 0000000000000000000000000000000000000000..6abdeac75dde2bbac8de3b1a7d75270d2396846e2454e9a57f185a45b5ee42b2
--- /dev/null
+++ b/main.go
@@ -0,0 +1,50 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"log"
+	"os"
+	"path"
+	"strings"
+)
+
+const MaxMsgLen = 1 << 20
+
+var (
+	DB, Host string
+	Args     []string
+)
+
+func main() {
+	log.SetFlags(0)
+	log.SetOutput(os.Stdout)
+	DB = os.Args[1]
+	Args = strings.Split(os.Getenv("SSH_ORIGINAL_COMMAND"), " ")
+	if Args[0] == "" {
+		fh, err := os.Open(path.Join(DB, "motd"))
+		if err != nil {
+			log.Fatal(err)
+		}
+		_, err = io.Copy(os.Stdout, bufio.NewReader(fh))
+		if err != nil {
+			log.Fatal(err)
+		}
+		return
+	}
+	var err error
+	switch Args[0] {
+	case "new":
+		err = doNew()
+	case "add":
+		err = doAdd()
+	case "get":
+		err = doGet()
+	default:
+		err = errors.New("unknown command supplied")
+	}
+	if err != nil {
+		log.Fatal(err)
+	}
+}
diff --git a/new.go b/new.go
new file mode 100644
index 0000000000000000000000000000000000000000..d88f6165c9a9d1ca6b546c3881906e87cb0e44299ac1e9f9216017ecf67ceec4
--- /dev/null
+++ b/new.go
@@ -0,0 +1,107 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+	"go.stargrave.org/recfile/v4"
+)
+
+func msgRead() ([]string, error) {
+	var buf bytes.Buffer
+	copied := make(chan error)
+	go func() {
+		_, err := io.CopyN(&buf, os.Stdin, MaxMsgLen)
+		if err == io.EOF {
+			copied <- nil
+			return
+		}
+		if err == nil {
+			copied <- errors.New("too large")
+			return
+		}
+	}()
+	t := time.NewTimer(time.Minute)
+	select {
+	case <-t.C:
+		return nil, errors.New("timeout")
+	case err := <-copied:
+		if err != nil {
+			return nil, err
+		}
+	}
+	return append([]string{""},
+		strings.Split(strings.TrimRight(buf.String(), "\n"), "\n")...), nil
+}
+
+func metaWrite(w *recfile.Writer) (err error) {
+	if _, err = w.RecordStart(); err != nil {
+		return err
+	}
+	if _, err = w.WriteFields(recfile.Field{
+		F: "when",
+		V: time.Now().Format("2006-01-02 15:04:05Z07:00"),
+	}); err != nil {
+		return err
+	}
+	if _, err = w.WriteFields(recfile.Field{
+		F: "from",
+		V: os.Getenv("SSH_CLIENT"),
+	}); err != nil {
+		return err
+	}
+	return nil
+}
+
+func doNew() error {
+	subj := strings.Join(Args[1:], " ")
+	if subj == "" {
+		return errors.New("empty subject")
+	}
+	body, err := msgRead()
+	if err != nil {
+		return err
+	}
+	id, err := uuid.NewV7()
+	if err != nil {
+		return err
+	}
+	fn := path.Join(DB, id.String()+".tmp")
+	fh, err := os.OpenFile(fn, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0o666)
+	if err != nil {
+		return err
+	}
+	defer os.Remove(fn)
+	defer fh.Close()
+	bw := bufio.NewWriter(fh)
+	w := recfile.NewWriter(bw)
+	if _, err = w.WriteFields(recfile.Field{F: "subj", V: subj}); err != nil {
+		return err
+	}
+	if err = metaWrite(w); err != nil {
+		return err
+	}
+	if _, err = w.WriteField("body", body); err != nil {
+		return err
+	}
+	if err = bw.Flush(); err != nil {
+		return err
+	}
+	if err = fh.Close(); err != nil {
+		return err
+	}
+	if err = os.Rename(fn, fn[:len(fn)-4]); err != nil {
+		return err
+	}
+	fmt.Println(id.String())
+	notify(id.String())
+	return nil
+}
diff --git a/notify.go b/notify.go
new file mode 100644
index 0000000000000000000000000000000000000000..cbc43a062d352c8662eb0eb1c37a1fa7c7934ccd701b3d5bf2913e510d4db87d
--- /dev/null
+++ b/notify.go
@@ -0,0 +1,38 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"path"
+	"strings"
+)
+
+const SendmailCmd = "/usr/sbin/sendmail"
+
+func notify(id string) {
+	var to string
+	{
+		data, err := os.ReadFile(path.Join(DB, "notify"))
+		if err != nil {
+			return
+		}
+		to = strings.TrimRight(string(data), "\n")
+	}
+	cmd := exec.Command(SendmailCmd, to)
+	cmd.Stdin = io.MultiReader(
+		strings.NewReader(fmt.Sprintf(
+			`From: msshg
+To: %s
+Subject: %s
+MIME-Version: 1.0
+Content-Type: text/plain; charset=utf-8
+
+`,
+			to, id,
+		)),
+		strings.NewReader(""),
+	)
+	cmd.Run()
+}