diff --git a/docs/email-delivery-brevo.md b/docs/email-delivery-brevo.md
new file mode 100644
index 00000000..f0ffa369
--- /dev/null
+++ b/docs/email-delivery-brevo.md
@@ -0,0 +1,16 @@
+# Email Deliverability Setup (Brevo & Outlook Junk Prevention)
+
+## Overview
+Default Firebase Authentication verification emails lack custom domain authentication and branded styling, causing aggressive filtering algorithms (especially Microsoft Outlook / Exchange / Office 365) to route verification emails to Junk.
+
+## Solution Architecture
+1. **Custom SMTP / Transactional Email Provider**: We integrate Brevo (`https://api.brevo.com/v3/smtp/email`) to send HTML branded verification messages with domain signing.
+2. **Domain Authentication Requirements**:
+   - **SPF**: Add `include:spf.brevo.com` to `mobilitydatabase.org` TXT records.
+   - **DKIM**: Add the DKIM TXT key provided in Brevo Domain Settings (`mail._domainkey.mobilitydatabase.org`).
+   - **DMARC**: Set a standard DMARC policy (e.g. `v=DMARC1; p=none; rua=mailto:dmarc@mobilitydata.org`).
+3. **Environment Variables**:
+   - `BREVO_API_KEY`: API key from Brevo console.
+   - `BREVO_SENDER_EMAIL`: Verified sender address (e.g. `no-reply@mobilitydatabase.org`).
+4. **Client Guidance**:
+   - The user verification page informs users to inspect their Junk/Spam folder and explicitly mark messages from `mobilitydatabase.org` as "Not Junk".
diff --git a/src/app/[locale]/verify-email/PostRegistration.tsx b/src/app/[locale]/verify-email/PostRegistration.tsx
index 26775780..46ba31b4 100644
--- a/src/app/[locale]/verify-email/PostRegistration.tsx
+++ b/src/app/[locale]/verify-email/PostRegistration.tsx
@@ -80,6 +80,11 @@ export default function PostRegistration(): React.ReactElement {
           account registration. Please also check your junk or spam folder if
           you do not see it in your inbox.
         </Box>
+        <Alert severity='info' sx={{ mt: 2 }}>
+          Using Microsoft Outlook or a corporate email? Verification emails may
+          land in your Junk folder. If found there, please mark the message as
+          &quot;Not Junk&quot; to ensure future notifications arrive safely.
+        </Alert>
         <Box sx={{ display: 'flex', justifyContent: 'center', mt: 2 }}>
           <Button
             variant='contained'
diff --git a/src/app/services/email-service.ts b/src/app/services/email-service.ts
new file mode 100644
index 00000000..1abed6c2
--- /dev/null
+++ b/src/app/services/email-service.ts
@@ -0,0 +1,99 @@
+/**
+ * Email Service for transactional emails (verification, notifications).
+ * Integrates with external email providers (such as Brevo / Sendinblue)
+ * to ensure high domain deliverability across corporate providers (Outlook/Office 365).
+ */
+
+export interface SendVerificationEmailPayload {
+  email: string;
+  displayName?: string;
+  verificationLink: string;
+}
+
+/**
+ * Sends a branded email verification message via external transactional email provider (Brevo API).
+ */
+export async function sendBrandedVerificationEmail(
+  payload: SendVerificationEmailPayload,
+): Promise<{ success: boolean; error?: string }> {
+  const apiKey = process.env.BREVO_API_KEY;
+  const senderEmail =
+    process.env.BREVO_SENDER_EMAIL ?? 'no-reply@mobilitydatabase.org';
+  const senderName = 'Mobility Database';
+
+  if (!apiKey) {
+    console.warn(
+      'BREVO_API_KEY not configured. Transactional email was not sent externally.',
+    );
+    return { success: false, error: 'BREVO_API_KEY is not configured.' };
+  }
+
+  try {
+    const htmlContent = `
+      <!DOCTYPE html>
+      <html>
+      <head>
+        <meta charset="utf-8">
+        <title>Verify your Mobility Database email</title>
+        <style>
+          body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif; background-color: #f4f5f7; margin: 0; padding: 24px; color: #172b4d; }
+          .container { max-width: 580px; margin: 0 auto; background: #ffffff; border-radius: 8px; overflow: hidden; box-shadow: 0 1px 3px rgba(0,0,0,0.1); }
+          .header { background-color: #003366; padding: 24px; text-align: center; }
+          .header h1 { color: #ffffff; margin: 0; font-size: 22px; }
+          .content { padding: 32px 24px; line-height: 1.6; }
+          .button { display: inline-block; background-color: #0066cc; color: #ffffff !important; padding: 12px 24px; text-decoration: none; border-radius: 4px; font-weight: bold; margin: 24px 0; }
+          .footer { background: #f9fafb; padding: 16px 24px; font-size: 12px; color: #6b778c; text-align: center; border-top: 1px solid #ebecf0; }
+        </style>
+      </head>
+      <body>
+        <div class="container">
+          <div class="header">
+            <h1>Mobility Database</h1>
+          </div>
+          <div class="content">
+            <p>Hello${payload.displayName ? ` ${payload.displayName}` : ''},</p>
+            <p>Thank you for signing up for the Mobility Database. Please confirm your email address by clicking the button below:</p>
+            <p style="text-align: center;">
+              <a href="${payload.verificationLink}" class="button" target="_blank" rel="noopener noreferrer">Verify Email Address</a>
+            </p>
+            <p>If the button doesn't work, you can copy and paste this link into your browser:</p>
+            <p style="word-break: break-all; font-size: 13px; color: #0066cc;">${payload.verificationLink}</p>
+            <p>If you did not request this email, no action is needed.</p>
+          </div>
+          <div class="footer">
+            &copy; ${new Date().getFullYear()} MobilityData. All rights reserved.<br />
+            If you are using Outlook or Office 365, please mark this message as "Not Junk" to ensure future delivery.
+          </div>
+        </div>
+      </body>
+      </html>
+    `;
+
+    const res = await fetch('https://api.brevo.com/v3/smtp/email', {
+      method: 'POST',
+      headers: {
+        accept: 'application/json',
+        'content-type': 'application/json',
+        'api-key': apiKey,
+      },
+      body: JSON.stringify({
+        sender: { name: senderName, email: senderEmail },
+        to: [{ email: payload.email, name: payload.displayName || payload.email }],
+        subject: 'Verify your Mobility Database email address',
+        htmlContent,
+      }),
+    });
+
+    if (!res.ok) {
+      const errText = await res.text();
+      return { success: false, error: `Brevo API error: ${errText}` };
+    }
+
+    return { success: true };
+  } catch (error) {
+    return {
+      success: false,
+      error: error instanceof Error ? error.message : 'Unknown email error',
+    };
+  }
+}
