diff --git a/README.md b/README.md
index a987060c..c33fe756 100644
--- a/README.md
+++ b/README.md
@@ -19,13 +19,14 @@ Some features:
     # Optional proxy, NO_PROXY is honored too:
     SMTP_PROXY: http://proxy.example.test:3128
   with:
-    # Specify connection via URL (replaces server_address, server_port, secure,
+    # Specify connection via URL (replaces server_address, server_port,
     # username and password)
     #
     # Format:
     #
     #  * smtp://user:password@server:port
-    #  * smtp+starttls://user:password@server:port
+    #  * smtps://user:password@server:port (TLS, default port 465)
+    #  * smtp+starttls://user:password@server:port (STARTTLS required, default port 587)
     connection_url: ${{secrets.MAIL_CONNECTION}}
 
     # Required mail server address if not connection_url:
diff --git a/action.yml b/action.yml
index ea0d3bb2..8d0fd64d 100644
--- a/action.yml
+++ b/action.yml
@@ -6,7 +6,7 @@ branding:
   color: blue
 inputs:
   connection_url:
-    description: Connection URL protocol://user:password@server:port, protocol can be smtp or smtp+starttls, replaces server_address, server_port, secure, username and password
+    description: Connection URL protocol://user:password@server:port, protocol can be smtp, smtps (TLS, default port 465) or smtp+starttls (STARTTLS required, default port 587), replaces server_address, server_port, username and password
   server_address:
     description: SMTP server address
   server_port:
diff --git a/main.js b/main.js
index 0819edaf..0bd9cc39 100644
--- a/main.js
+++ b/main.js
@@ -93,15 +93,13 @@ async function main() {
     try {
         let serverAddress = core.getInput("server_address");
         let serverPort = core.getInput("server_port");
-        let secure = core.getInput("secure");
-        const requireTLS = core.getInput("require_tls", { required: false });
+        let secure = core.getInput("secure")
+            ? core.getBooleanInput("secure")
+            : undefined;
+        let requireTLS = core.getInput("require_tls", { required: false });
         let username = core.getInput("username");
         let password = core.getInput("password");
 
-        if (!secure) {
-            secure = serverPort === "465" ? "true" : "false";
-        }
-
         const connectionUrl = core.getInput("connection_url");
         if (connectionUrl) {
             const url = new URL(connectionUrl);
@@ -112,11 +110,15 @@ async function main() {
                     );
                 case "smtp:":
                     serverPort = "25";
-                    secure = "false";
+                    break;
+                case "smtps:":
+                    serverPort = "465";
+                    secure = true;
                     break;
                 case "smtp+starttls:":
-                    serverPort = "465";
-                    secure = "true";
+                    serverPort = "587";
+                    secure = false;
+                    requireTLS = "true";
                     break;
             }
             if (url.hostname) {
@@ -133,6 +135,10 @@ async function main() {
             }
         }
 
+        if (secure === undefined) {
+            secure = serverPort === "465";
+        }
+
         const subject = core.getInput("subject", { required: true });
         const from = core.getInput("from", { required: true });
         const to = core.getInput("to", { required: false });
@@ -196,7 +202,7 @@ async function main() {
                       }
                     : undefined,
             port: serverPort,
-            secure: secure === "true",
+            secure: secure,
             requireTLS: requireTLS === "true",
             tls:
                 ignoreCert == "true"