diff --git a/tests/unit/test_email_gateway.py b/tests/unit/test_email_gateway.py
new file mode 100644
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+++ b/tests/unit/test_email_gateway.py
@@ -0,0 +1,170 @@
+#!/usr/bin/env python3
+
+# Libervia: an XMPP client
+# Copyright (C) 2009-2024 Jérôme Poisson (goffi@goffi.org)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# 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 Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from email.utils import formataddr
+from unittest.mock import AsyncMock, MagicMock
+import pytest
+from pytest_twisted import ensureDeferred as ed
+from twisted.words.protocols.jabber import jid
+from email.message import EmailMessage
+from libervia.backend.plugins.plugin_comp_email_gateway import EmailGatewayComponent
+from libervia.backend.plugins.plugin_comp_email_gateway.models import (
+    Credentials,
+    UserData,
+)
+
+
+class TestEmailGatewayComponent:
+    @pytest.fixture
+    def email_gw(self, host):
+        email_gw = EmailGatewayComponent(host)
+        email_gw.storage = MagicMock()
+        email_gw.users_data = {}
+        return email_gw
+
+    def test_jid_to_email_gateway_jid(self, email_gw):
+        """JID from the gateway is converted to an email address."""
+        client = MagicMock()
+        client.jid = jid.JID("gateway.example.org")
+        address_jid = jid.JID(r"user\40some-email-domain.example@gateway.example.org")
+        credentials = {"user_email": "user@example.org"}
+        result = email_gw.jid_to_email(client, address_jid, credentials)
+        assert result == "user@some-email-domain.example"
+
+    def test_jid_to_email_non_gateway_jid(self, email_gw):
+        """Non-gateway JID is converted to an email address with ``xmpp:``."""
+        client = MagicMock()
+        client.jid = jid.JID("gateway.example.org")
+        address_jid = jid.JID("external@example.org")
+        credentials = {"user_email": "user@example.org"}
+        result = email_gw.jid_to_email(client, address_jid, credentials)
+        assert result == '"xmpp:external@example.org" <user@example.org>'
+
+    def test_email_to_jid_user_email(self, email_gw):
+        """User email returns user JID if no "xmpp:" scheme is used."""
+        client = MagicMock()
+        client.jid = jid.JID("gateway.example.org")
+        email_name = ""
+        email_addr = "user@example.org"
+        user_email = "user@example.org"
+        user_jid = jid.JID("gw-user@example.org")
+        result, name = email_gw.email_to_jid(
+            client, user_email, user_jid, email_name, email_addr
+        )
+        assert result == jid.JID("gw-user@example.org")
+        assert name is None
+
+    def test_email_to_jid_xmpp_address(self, email_gw):
+        """Email address with XMPP in name part is converted to a JID."""
+        client = MagicMock()
+        client.jid = jid.JID("gateway.example.org")
+        email_name = "xmpp:user@example.net"
+        email_addr = "user@example.org"
+        user_email = "user@example.org"
+        user_jid = jid.JID("gw-user@example.org")
+        result, name = email_gw.email_to_jid(
+            client, user_email, user_jid, email_name, email_addr
+        )
+        assert result == jid.JID("user@example.net")
+        assert name is None
+
+    def test_email_to_jid_regular_email(self, email_gw):
+        """Regular email address is converted to a JID with escaped local part."""
+        client = MagicMock()
+        client.jid = jid.JID("gateway.example.org")
+        email_name = "User Name"
+        email_addr = "user@some-email-domain.example"
+        user_email = "user@example.org"
+        user_jid = jid.JID("gw-user@example.org")
+        result, name = email_gw.email_to_jid(
+            client, user_email, user_jid, email_name, email_addr
+        )
+        assert result == jid.JID(r"user\40some-email-domain.example@gateway.example.org")
+        assert name == "User Name"
+
+    @ed
+    async def test_on_new_email_single_recipient(self, email_gw):
+        """Email with a single recipient is correctly processed and sent as a message."""
+        client = MagicMock()
+        client.get_virtual_client = lambda __: client
+        client.jid = jid.JID("gateway.example.org")
+        client.sendMessage = AsyncMock()
+        email_gw.client = client
+
+        email = EmailMessage()
+        email["from"] = formataddr(("User Name", "sender@somewhere.example"))
+        email["to"] = "user@example.org"
+        email.set_content("Hello, world!")
+
+        to_jid = jid.JID("gw-user@example.org")
+        user_email = "user@example.org"
+        user_data = UserData(Credentials({"user_email": user_email}))
+        await email_gw.on_new_email(user_data, to_jid, email)
+
+        client.sendMessage.assert_called_once()
+        call_args = client.sendMessage.call_args[0]
+        assert call_args[0] == to_jid
+        assert call_args[1] == {"": "Hello, world!\n"}
+        assert call_args[2] == None
+        client.sendMessage.assert_called_once_with(
+            to_jid, {"": "Hello, world!\n"}, None, extra=None
+        )
+
+    @ed
+    async def test_on_new_email_multiple_recipients(self, email_gw):
+        """Email with multiple recipients is correctly processed and sent ."""
+        client = MagicMock()
+        client.get_virtual_client = lambda __: client
+        client.jid = jid.JID("gateway.example.org")
+        client.sendMessage = AsyncMock()
+        email_gw.client = client
+
+        email = EmailMessage()
+        email["from"] = formataddr(("User Name", "user@example.org"))
+        email["to"] = "user@example.org"
+        email["cc"] = "recipient2@example.org"
+        email["bcc"] = "recipient3@example.org"
+        email.set_content("Hello, world!")
+
+        user_jid = jid.JID("gw-user@example.org")
+        user_email = "user@example.org"
+        user_data = UserData(Credentials({"user_email": user_email}))
+        await email_gw.on_new_email(user_data, user_jid, email)
+
+        client.sendMessage.assert_called_once_with(
+            user_jid,
+            {"": "Hello, world!\n"},
+            None,
+            extra={
+                "addresses": {
+                    "to": [{"jid": "gw-user@example.org", "delivered": True}],
+                    "cc": [
+                        {
+                            "jid": "recipient2\\40example.org@gateway.example.org",
+                            "delivered": True,
+                        }
+                    ],
+                    "bcc": [
+                        {
+                            "jid": "recipient3\\40example.org@gateway.example.org",
+                            "delivered": True,
+                        }
+                    ],
+                }
+            },
+        )