diff --git a/src/mail.js b/src/mail.js
index eead642..4996b6f 100644
--- a/src/mail.js
+++ b/src/mail.js
@@ -40,6 +40,7 @@ export const mail = async ({ env = {}, ...rest }) => {
       attachments: !!rest.attachments,
       contentType: rest.type,
       status: response.status,
+      userAgent: rest.userAgent,
     },
   });
   if (response.status > 299) {
diff --git a/src/mail.test.js b/src/mail.test.js
index f4d3c69..898ba00 100644
--- a/src/mail.test.js
+++ b/src/mail.test.js
@@ -47,7 +47,11 @@ describe('mail', () => {
   });
   it('logs', async () => {
     global.fetch.mockResolvedValue({ json: () => '{}', status: 200 });
-    await mail({ ...input, to: 'one@example.com,two@example.com' });
+    await mail({
+      ...input,
+      to: 'one@example.com,two@example.com',
+      userAgent: 'custom-user-agent 1.0',
+    });
     expect(global.fetch).toHaveBeenCalledWith(
       'https://api.logsnag.com/v1/log',
       expect.objectContaining({
@@ -61,6 +65,7 @@ describe('mail', () => {
             attachments: true,
             contentType: 'text/html',
             status: 200,
+            userAgent: 'custom-user-agent 1.0',
           },
         }),
       }),
diff --git a/src/params.js b/src/params.js
index 759cb11..01a4922 100644
--- a/src/params.js
+++ b/src/params.js
@@ -34,6 +34,8 @@ export const params = async (request) => {
     // pass
   }
 
+  data.userAgent = request.headers.get('user-agent');
+
   data.errors = required.reduce(
     (acc, el) =>
       data?.[el] ? acc : [...acc, `missing required parameter '${el}'`],
diff --git a/src/params.test.js b/src/params.test.js
index de2eef1..24f4bbb 100644
--- a/src/params.test.js
+++ b/src/params.test.js
@@ -20,6 +20,7 @@ describe.each(['application/json', 'application/x-www-form-urlencoded'])(
         method: 'POST',
         headers: {
           'Content-Type': contentType,
+          'User-Agent': 'custom-user-agent 1.0',
         },
         body: (format[contentType] ?? ((d) => d))(body),
       });
@@ -27,6 +28,7 @@ describe.each(['application/json', 'application/x-www-form-urlencoded'])(
       expect(await params(request)).toEqual({
         errors: [],
         ...body,
+        userAgent: 'custom-user-agent 1.0',
       });
     });