Custom SMTP & Domain Authentication Guide

FormMail Hub utilizes a flexible dual-transport model to deliver administrative system alerts and client-facing custom outreach via its independent cloud platform engine.

Understanding when Custom SMTP is required—and testing credentials to unlock feature tabs—is essential for leveraging full platform capabilities. You can test form submit workflows on our Live Demo Form or install the add-on directly via the Google Workspace Marketplace Listing.

1. Built-in System SMTP Scope vs. Custom SMTP Requirement

+-----------------------------------------------------------------------------------+
|                        DELIVERY SYSTEM CONFIGURATION PATH                         |
+-----------------------------------------------------------------------------------+
                                  |
          +-----------------------+-----------------------+
          |                                               |
          v                                               v
+-----------------------------------+           +-----------------------------------+
|     BUILT-IN SYSTEM SMTP RELAY    |           |    CUSTOM SMTP INTEGRATION        |
+-----------------------------------+           +-----------------------------------+
| - RESTRICTED strictly to system   |           | - MANDATORY setup & test BEFORE   |
|   alerts (submission alerts,      |           |   unlocking Templates, Rules,     |
|   daily reports, SMTP error alerts)|           |   Campaigns, or Analytics         |
|   to Admin & Team Members         |           | - Feature tabs strictly locked in |
| - CANNOT send custom templates or |           |   UI until Custom SMTP is active  |
|   respondent auto-responders      |           | - Responders, rules, campaigns    |
+-----------------------------------+           +-----------------------------------+

Built-in System SMTP Scope

Built-in System SMTP is STRICTLY restricted to sending system alerts (submission notifications, daily activity reports, and SMTP connection error alerts) to the Form Admin and selected Team Members. System SMTP CANNOT be used for custom templates, rule-based notifications, or respondent auto-responders.

Absolute Custom SMTP Requirement & UI Lock State

Admins MUST configure and test custom SMTP settings before unlocking Templates, Rules, Campaigns, or Analytics. Until custom SMTP is active, these feature tabs remain strictly locked in the UI.

2. Step-by-Step Provider Setup Guides

Provider A: Google Workspace & Gmail™ App Passwords

To send emails under your Google identity without hitting native Apps Script restrictions, generate a Google App Password.

Enable 2-Step Verification: Go to Google Account Security (myaccount.google.com/security) and ensure 2-Step Verification is ON.
Generate App Password: Search for App Passwords, enter FormMail Hub, and copy the generated 16-character secret key.
Configure & Test in FormMail Hub:
- Navigate to Settings > SMTP Config.
- Host: smtp.gmail.com
- Port: 587 (TLS) or 465 (SSL)
- Username: Your full Gmail/Workspace email address.
- Password: The 16-character App Password (without spaces).
- Test Connection: Click Test Connection to verify settings and unlock the UI tabs (Templates, Rules, Campaigns, Analytics).

Provider B: Amazon SES (Simple Email Service)

Verify Identity: In the AWS SES Console, create and verify your sending domain identity via CNAME records.
Generate SMTP Credentials: Navigate to SES > Account Level Settings > SMTP Settings and click Create SMTP Credentials.
Request Production Access: Request exit from the AWS SES Sandbox environment.
Configure & Test in FormMail Hub:
- Navigate to Settings > SMTP Config.
- Host: email-smtp.{region}.amazonaws.com (e.g., email-smtp.us-east-1.amazonaws.com)
- Port: 587 (TLS)
- Username / Password: AWS SES IAM SMTP credentials.
- Test Connection: Test settings to unlock locked UI feature tabs.

Provider C: SendGrid / Mailgun / Custom Corporate Relays

SendGrid: Host smtp.sendgrid.net, Port 587, Username apikey, Password = Your API Key.
Mailgun: Host smtp.mailgun.org, Port 587, Username = Postmaster address, Password = SMTP password.
Custom Relay: Input corporate host (smtp.yourdomain.com), port (587 or 465), and authorized user credentials under Settings > SMTP Config.
Test Connection: Test credentials to verify transport and unlock UI feature tabs.

3. Domain Authentication (SPF, DKIM & DMARC)

To ensure high inbox placement when sending via Custom SMTP, configure DNS records at your domain host:

SPF (Sender Policy Framework):

v=spf1 include:amazonses.com include:_spf.google.com ~all

DKIM (DomainKeys Identified Mail): Publish the CNAME/TXT keys generated by Amazon SES, SendGrid, or Google Workspace.

DMARC:

v=DMARC1; p=none; rua=mailto:dmarc-reports@yourdomain.com

4. Diagnostics & Connection Troubleshooting

Error Code	Primary Cause	Resolution
`FAILED_SMTP_AUTH` / `535 5.7.8`	Invalid username or account password used instead of App Password.	Re-enter credentials under Settings > SMTP Config. For Gmail accounts, generate a dedicated 16-character App Password and test connection.
`FAILED_SMTP_CONNECT`	Host port blocked by network firewall or wrong hostname.	Switch connection port from 25 to 587 (TLS) or 465 (SSL).
`Feature Access Locked`	Custom SMTP not configured or tested.	Admins MUST configure and test custom SMTP settings under Settings > SMTP Config before unlocking Templates, Rules, Campaigns, or Analytics.

5. Official Resources & Compliance

Need assistance with connection diagnostics? Access our official support channels:

Technical Assistance: Support & Contact
Legal & Privacy Policies: Review our Privacy Policy and Terms of Service.

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