diff --git a/docs/configuring-playbook-email.md b/docs/configuring-playbook-email.md
index b308b6b4..5f386ef3 100644
--- a/docs/configuring-playbook-email.md
+++ b/docs/configuring-playbook-email.md
@@ -18,4 +18,8 @@ matrix_mailer_relay_host_port: 587
 matrix_mailer_relay_auth: true
 matrix_mailer_relay_auth_username: "another.sender@example.com"
 matrix_mailer_relay_auth_password: "some-password"
-```
\ No newline at end of file
+```
+
+**Note**: no matter whether you relay email through another host (by defining `matrix_mailer_relay_host_name`) or you let the local (in-container) postfix deliver directly, you'll probably need to allow outgoing traffic for TCP ports 25/587 (depending on configuration).
+
+If you're having trouble with email not being delivered, it may be useful to inspect the mailer logs: `journalctl -f -u matrix-mailer`.
\ No newline at end of file