How to Set Up Gmail SMTP for AI Email Replies in Mail AI

📧 Gmail SMTP ⏱ 5 Min Setup Updated: April 4, 2026 • By the Mail AI Team

When a client emails your business, your Gmail AI Agent reads it, summarises it with AI, and lets you reply with a single click — right from the dashboard. But for that reply to land in your client's inbox from your actual Gmail address, you need to connect Gmail SMTP.

This guide walks you through the exact steps. The whole process takes under 5 minutes, and you only need to do it once per Gmail address.

💡 Before you start: Make sure you have already set up Gmail forwarding and linked your Gmail address in the Mail AI dashboard. SMTP is the outbound (reply) layer — forwarding is the inbound (receive) layer.

What is SMTP and Why Do You Need It?

SMTP (Simple Mail Transfer Protocol) is the industry-standard protocol for sending email. Without it, Mail AI can receive and read your emails, but cannot send replies on your behalf.

When you configure Gmail SMTP in Mail AI:

Gmail SMTP Settings at a Glance

Setting Value
SMTP Host smtp.gmail.com Copy
Port 587
Encryption STARTTLS
Username Your full Gmail address (e.g. [email protected])
Password Your App Password (NOT your Google login password)
⚠️ Important: Gmail blocks standard password login for third-party apps. You must generate an App Password — a separate 16-character code — for Mail AI to work. Your main Google password will not work here.

Step-by-Step Setup

  1. 1
    Enable 2-Step Verification on your Google Account

    Sign in to myaccount.google.com → Security → 2-Step Verification → Turn On. Gmail App Passwords only work when 2FA is active.

    Open Google Account Settings →
  2. 2
    Generate a Gmail App Password

    Go to myaccount.google.com/apppasswords → Select app: Mail → Select device: Other → type "MailAI" → Click Generate. Copy the 16-character password shown.

    Open Google Account Settings →
  3. 3
    Open Reply SMTP Setting in Mail AI

    In your Mail AI dashboard, go to Linked Email Accounts. Find your Gmail address and click "+ Reply SMTP Setting".

  4. 4
    Select Gmail as provider and enter credentials

    Choose Gmail from the provider list. Enter your full Gmail address as the username. Paste the 16-character App Password (not your Google login password). SMTP host, port (587), and STARTTLS are pre-filled automatically.

  5. 5
    Save and verify the connection

    Click Save SMTP. Mail AI will test the connection instantly. A green "Custom SMTP ✓" badge appears on your linked email when successful.

✅ Success looks like: After saving, your linked email card in the Mail AI dashboard will show a green "Custom SMTP ✓" badge. Any Gmail AI Reply you send from that point will be delivered directly from your Gmail address.

Troubleshooting Common Gmail SMTP Errors

"Authentication Failed" or "Username/Password Incorrect"

This almost always means you entered your regular Google password instead of the 16-character App Password. Go back to myaccount.google.com/apppasswords, generate a new one, and paste it carefully — no spaces.

"App Passwords" option is not visible in my Google Account

App Passwords only appear after enabling 2-Step Verification. If your account is a Google Workspace (business/school) account, ask your admin to allow App Passwords under Admin Console → Security → Less Secure App Access, or use Brevo SMTP as an alternative.

SMTP test succeeds but replies are not being sent

Check that the "From Email" in your SMTP settings matches the Gmail address exactly (including capitalisation). Also verify your linked email address in Mail AI matches the Gmail address you set up forwarding from.

Emails land in spam at the recipient's end

This is a Gmail deliverability question, not a Mail AI issue. Ensure your Gmail account is warmed up (active for at least 30 days), avoid spam-trigger words in subjects, and consider moving to Brevo for better transactional deliverability.

Gmail SMTP vs Other Providers

Mail AI supports multiple SMTP providers. Here's when to use Gmail versus the alternatives:

Ready to Start Replying?

With Gmail SMTP connected, your entire workflow is complete: emails arrive from your clients, Mail AI reads and summarises them, the AI Agent for Gmail drafts a reply using your knowledge base — and when you click Send, it leaves from your own Gmail address.

No switching tabs. No copy-pasting. No missed messages.

Go to your Mail AI dashboard →

Related Setup Guides

📬 How to Set Up Gmail Forwarding
Route incoming Gmail to your Mail AI inbox
💚 Brevo SMTP Setup Guide
Best for custom domain email addresses
🟠 ZeptoMail SMTP Setup Guide
High-volume transactional replies
🟣 Amazon SES SMTP Setup
Enterprise-scale email delivery

Frequently Asked Questions

Why does Gmail need an App Password instead of my normal password?
Google blocks third-party apps from using your main password directly for security reasons. An App Password is a special 16-character code that grants Mail AI limited SMTP access only — it cannot log into your Google account or access any other Google services. You can revoke it at any time.
What if I don't see the App Passwords option in my Google Account?
App Passwords only appear when 2-Step Verification is enabled on your account. If you use Google Workspace (a work or school account), your administrator may have disabled this feature. In that case, use Brevo or another SMTP provider instead.
Can I use Gmail SMTP to send replies from a custom domain email like [email protected]?
No. Gmail SMTP only sends from your @gmail.com address. If you want to send from a custom domain address (like [email protected]), use Brevo, ZeptoMail, or your cPanel/hosting SMTP instead — all of which are supported in Mail AI.
Will my clients see that emails come from MailAI?
No. When you reply through Mail AI with Gmail SMTP configured, your clients receive the email directly from your Gmail address. It looks and threads exactly like a normal Gmail message. Mail AI is completely invisible to the recipient.
How many emails can I send per day with Gmail SMTP?
Google allows up to 500 emails per day through Gmail SMTP for standard @gmail.com accounts, and up to 2,000 per day for Google Workspace accounts. For high-volume business replies, consider Brevo (300 free emails/day) or ZeptoMail.
Is it safe to give Mail AI my App Password?
Yes. App Passwords are stored encrypted (AES-256-CBC) in Mail AI's database and are never visible after you save them — not even in plain text. You can revoke the App Password from your Google Account at any time without affecting your main Google login.