diff --git a/roles/mail_forwarder/molecule/default/tests/test_optional.py b/roles/mail_forwarder/molecule/default/tests/test_optional.py
index d0375369d89ca382de7f772b4fd57381708d061b..ea1441c69781911a5a1cfa627dd1aba3629d4f20 100644
--- a/roles/mail_forwarder/molecule/default/tests/test_optional.py
+++ b/roles/mail_forwarder/molecule/default/tests/test_optional.py
@@ -126,3 +126,17 @@ def test_tls_enforced_towards_relay_mail_server(host):
             pattern = r"%s: to=<root@domain1>, relay=domain1.*status=deferred \(Server certificate not verified\)" % message_id
 
             assert re.search(pattern, mail_log.content_string) is not None
+
+
+def test_mail_message_size_limit(host):
+    """
+    Tests if the mail message size limit advertised by the SMTP server
+    is correct.
+    """
+
+    capabilities = host.run("(echo 'ehlo localhost' && sleep 2) | telnet localhost 25")
+    begin = capabilities.stdout.find("250-SIZE")
+    end = capabilities.stdout.find("\n", begin)
+    mail_message_size_limit = capabilities.stdout[begin:end]
+
+    assert mail_message_size_limit == "250-SIZE 20480001"