? Introduction

Email remains the backbone of professional communication. Whether you're managing multiple business inboxes or ensuring reliable message delivery, having a secure and consistent SMTP (Simple Mail Transfer Protocol) setup is essential.

If you’re a Google Workspace (formerly G Suite) user and using a third-party service like QLC or another SMTP host, you can simplify everything by configuring Google’s own built-in SMTP service directly within your email client — such as Postbox, Outlook, or Thunderbird.

This article, prepared by Bison Infosolutions Pvt. Ltd., explains how to configure Google Workspace SMTP in Postbox with step-by-step instructions, common troubleshooting tips, and the major benefits of switching from external SMTP services to Google’s native infrastructure.

? What Is Google Workspace SMTP?

SMTP (Simple Mail Transfer Protocol) is the standard protocol for sending outgoing emails.
Google Workspace provides two SMTP options for its users:

1. Per-User Authenticated SMTP (smtp.gmail.com)
   Each user authenticates individually using their Google Workspace email credentials.
   This is ideal for personal or desktop mail clients like Postbox, Outlook, or Apple Mail.

2. Google Workspace SMTP Relay (smtp-relay.gmail.com)
   Designed for servers, CRMs, or internal systems that send messages on behalf of users.
   This method allows domain-level control via IP authentication and security policies.

Both are included in your Workspace subscription at no extra cost — offering security, reliability, and unmatched deliverability.

? Why Replace Third-Party SMTP Services like QLC

Many businesses use external SMTP providers such as QLC, SendGrid, or custom relays for sending emails.
However, Google’s native SMTP eliminates the need for intermediaries by offering:

• ✔️ Direct integration with Google Workspace

• ✔️ Enterprise-grade encryption (TLS/SSL)

• ✔️ SPF, DKIM, and DMARC alignment for spam-free delivery

• ✔️ Sent mail synchronization across all devices

• ✔️ Cost efficiency (no additional hosting or relay charges)

When using third-party relays, users often face issues like messages being sent from the wrong account, authentication conflicts, or mismatched sender identities — which Google’s direct SMTP setup solves elegantly.

? Step-by-Step Setup of Google Workspace SMTP in Postbox

Step 1: Enable IMAP in Gmail

1. Log in to your Gmail Workspace account.

2. Click the ⚙️ Settings icon → See all settings → Forwarding and POP/IMAP.

3. Under IMAP Access, choose Enable IMAP.

4. Save changes.

Step 2: Enable 2-Step Verification and Create an App Password

1. Go to https://myaccount.google.com/security.

2. Under “Signing in to Google”, turn on 2-Step Verification.

3. Once active, click App Passwords.

4. Select “Mail” as the app and “Computer” as the device, then click Generate.

5. Copy the 16-character password — this replaces your regular Google password in Postbox.

Step 3: Configure the Account in Postbox

1. Open Postbox → File → New → Mail Account.

2. Enter:

   • Name: Your full name

   • Email address: yourname@yourdomain.com

   • Password: App Password (generated above)

3. Postbox automatically detects Gmail settings. Verify the following:

   SMTP Server: smtp.gmail.com
   Port: 587
   Encryption: STARTTLS
   Authentication: OAuth2 or Normal Password
   Username: your full email address
   

Step 4: Assign Separate SMTP Server for Each Account

In Postbox → Preferences → Accounts → Outgoing Server (SMTP):
Make sure each Workspace email (sales@, accounts@, info@) uses its own dedicated SMTP entry.
This prevents the common problem of messages being sent through the wrong mailbox.

Step 5: Test and Verify

Send a test email to yourself.
Open the received message → click Show Original → look for this line:

Received-SPF: pass (google.com: domain of yourname@yourdomain.com designates 209.85.x.x as permitted sender)

If you see “pass”, your setup is verified.

⚙️ Optional: Google Workspace SMTP Relay Setup

For bulk or system-generated emails (like from billing software, CRMs, or ERP tools):

1. Sign in to Google Admin Console.

2. Navigate to:
   Apps → Google Workspace → Gmail → Routing → SMTP Relay Service.

3. Click Add Setting, name it (e.g., Company Relay).

4. Configure:

   • Allowed senders: Only addresses in my domains

   • Authentication: Only accept from specified IP addresses

   • Encryption: TLS required

5. Save settings and use:

   SMTP Server: smtp-relay.gmail.com
   Port: 587
   TLS: Enabled
   

? Troubleshooting Common Issues

? Advantages of Using Google SMTP

• Fully integrated with Google Workspace

• Secure OAuth2 authentication

• Consistent delivery and branding

• Automatic synchronization of sent emails

• No dependency on external SMTP vendors

• Improved trust and sender reputation

• Zero additional cost

? About Bison Infosolutions Pvt. Ltd.

Bison Infosolutions is a trusted provider of IT services, AMC solutions, cloud infrastructure, and business email management systems.
We specialize in Google Workspace, Microsoft 365, hosting, Tally on Cloud, and professional IT support for businesses of all sizes.

For professional assistance in setting up your email systems or transitioning from third-party SMTP services to Google Workspace, contact us:
? +91-9212522725 | +91-7047947970 | +91-7658858876
✉️ info@bison.co.in
? www.bison.co.in

? Conclusion

Switching from external SMTP providers like QLC to Google Workspace’s own SMTP service ensures higher security, simpler configuration, and total control over your organization’s email flow.
Postbox users can enjoy seamless sending, perfect identity matching, and guaranteed Google-level reliability — all without any additional costs or complications.

By following this guide, businesses can manage their emails more efficiently, avoid routing errors, and ensure that every outgoing message reflects their professional identity accurately.