diff --git a/projekt-matching/projektmatch/mailer.py b/projekt-matching/projektmatch/mailer.py
index 9dbdd0b..4ed2a09 100644
--- a/projekt-matching/projektmatch/mailer.py
+++ b/projekt-matching/projektmatch/mailer.py
@@ -71,6 +71,39 @@ class MailBox:
             pass
 
 
+def _sent_folder(conn):
+    """Find the server's Sent folder via special-use flag, fallback names."""
+    typ, data = conn.list()
+    candidates = []
+    for raw in data or []:
+        line = raw.decode() if isinstance(raw, bytes) else str(raw)
+        name = line.rsplit(" ", 1)[-1].strip('"')
+        if "\\Sent" in line.split(")")[0]:
+            return name
+        candidates.append(name)
+    for cand in ("Sent", "INBOX.Sent"):
+        if cand in candidates:
+            return cand
+    return "Sent"
+
+
+def append_sent(user, password, msg, conn=None):
+    """Store a copy of an outgoing message in the Sent folder (best effort)."""
+    own = conn is None
+    conn = conn or imaplib.IMAP4_SSL(IMAP_HOST, IMAP_PORT)
+    try:
+        if own:
+            conn.login(user, password)
+        folder = _sent_folder(conn)
+        conn.append(folder, "(\\Seen)", None, msg.as_bytes())
+    finally:
+        if own:
+            try:
+                conn.logout()
+            except Exception:
+                pass
+
+
 def send_mail(user, password, to, subject, body):
     msg = EmailMessage()
     msg["From"], msg["To"], msg["Subject"] = user, to, subject
@@ -81,3 +114,7 @@ def send_mail(user, password, to, subject, body):
         server.starttls(context=ssl.create_default_context())
         server.login(user, password)
         server.send_message(msg)
+    try:
+        append_sent(user, password, msg)
+    except Exception:      # noqa: BLE001 — copy is best effort; the mail went out
+        pass
diff --git a/projekt-matching/tests/test_mailer.py b/projekt-matching/tests/test_mailer.py
index b29227a..a1e4119 100644
--- a/projekt-matching/tests/test_mailer.py
+++ b/projekt-matching/tests/test_mailer.py
@@ -1,4 +1,5 @@
 import email
+from email.message import EmailMessage
 
 import pytest
 from unittest import mock
@@ -62,7 +63,8 @@ def test_fetch_raises_on_malformed_ok_response():
 
 
 def test_send_mail_starttls():
-    with mock.patch("projektmatch.mailer.smtplib.SMTP") as smtp:
+    with mock.patch("projektmatch.mailer.smtplib.SMTP") as smtp, \
+            mock.patch("projektmatch.mailer.append_sent") as append_sent:
         server = smtp.return_value.__enter__.return_value
         mailer.send_mail("u@x", "pw", "to@x", "Subj", "Body")
     server.starttls.assert_called_once()
@@ -71,3 +73,30 @@ def test_send_mail_starttls():
     assert msg["Subject"] == "Subj" and msg["To"] == "to@x"
     assert msg["Date"]
     assert msg["Message-ID"].endswith("@destengs.com>")
+    append_sent.assert_called_once_with("u@x", "pw", msg)
+
+
+def test_send_mail_survives_append_failure():
+    with mock.patch("projektmatch.mailer.smtplib.SMTP") as smtp, \
+            mock.patch("projektmatch.mailer.append_sent",
+                        side_effect=OSError("imap down")):
+        mailer.send_mail("u@x", "pw", "to@x", "Subj", "Body")
+
+
+def test_append_sent_uses_special_use_folder():
+    conn = mock.Mock()
+    conn.list.return_value = ("OK", [
+        b'(\\HasNoChildren) "." "INBOX"',
+        b'(\\HasNoChildren \\Sent) "." "Sent"'])
+    msg = EmailMessage()
+    msg["Subject"] = "Subj"
+    msg.set_content("Body")
+
+    mailer.append_sent("u@x", "pw", msg, conn=conn)
+
+    args = conn.append.call_args.args
+    assert args[0] == "Sent"
+    assert "\\Seen" in args[1]
+    assert args[3] == msg.as_bytes()
+    conn.login.assert_not_called()
+    conn.logout.assert_not_called()