diff --git a/asciinema/compose.yaml b/asciinema/compose.yaml
index 83bd437..46b5160 100644
--- a/asciinema/compose.yaml
+++ b/asciinema/compose.yaml
@@ -7,6 +7,7 @@ services:
       - compose_network
     volumes:
       - asciinema_data:/var/opt/asciinema
+      - ./custom.exs:/opt/app/etc/custom.exs:ro
     environment:
       SECRET_KEY_BASE: ${ASCIINEMA_SECRET_KEY}
       URL_HOST: ${ASCIINEMA_TRAEFIK_HOST}
@@ -19,7 +20,7 @@ services:
       MAIL_FROM_ADDRESS: ${EMAIL_FROM}
       # SMTP_PORT: 465
       SMTP_SSL: false
-      SMTP_TLS: always
+      SMTP_TLS: false
       SMTP_AUTH: always
       SMTP_NO_MX_LOOKUPS: false
       SIGN_UP_DISABLED: ${ASCIINEMA_SIGN_UP_DISABLED:-false}
diff --git a/asciinema/custom.exs b/asciinema/custom.exs
new file mode 100644
index 0000000..dd1b726
--- /dev/null
+++ b/asciinema/custom.exs
@@ -0,0 +1,17 @@
+import Config
+
+# Configure Swoosh SMTP adapter to skip TLS certificate verification
+# This is needed for IONOS SMTP server which has certificate key usage issues
+config :asciinema, Asciinema.Emails.Mailer,
+  adapter: Swoosh.Adapters.SMTP,
+  relay: System.get_env("SMTP_HOST"),
+  username: System.get_env("SMTP_USERNAME"),
+  password: System.get_env("SMTP_PASSWORD"),
+  port: System.get_env("SMTP_PORT") || 587,
+  tls: :always,
+  auth: :always,
+  ssl: false,
+  tls_options: [
+    verify: :verify_none,
+    versions: [:"tlsv1.2", :"tlsv1.3"]
+  ]