Overview
The Custom SMTP Sending Address feature allows organizations to send email campaigns through their own mail servers rather than through PublicInput's default SendGrid infrastructure. This is a more advanced approach relative to sending email through a custom domain, which allows for multiple addresses on a given domain.
This feature is gated by the customer's feature plan.
Use Cases
When to Use Custom SMTP Sending
Compliance Requirements: Organizations with policies requiring all outbound email to route through their mail infrastructure
Audit Trail: Organizations needing all emails logged in their own mail server logs
When to Use Standard Custom Email Sending Domain Authentication
For most clients, the standard Custom Email Sending Domains feature (SendGrid-based) is sufficient. This option:
Allows emails to be flexibly sent FROM your domain (e.g.,
updates@yourcity.gov)Uses PublicInput's reliable email infrastructure and analytics
Requires only DNS CNAME record configuration
Provides delivery tracking and analytics
SMTP Address Setup Instructions
Prerequisites
Before configuring a custom SMTP sending address, you'll need the following from your IT department:
Requirement | Description | Example |
SMTP Host | The mail server hostname |
|
SMTP Port | The port for SMTP connections |
|
SMTP Username | Authentication username | Often the full email address |
SMTP Password | Authentication password | Service account password |
From Address | The email address to send from |
|
Common SMTP Configurations
Provider | Host | Port | Notes |
Microsoft 365 |
| 587 | Requires authenticated user |
Google Workspace |
| 587 | Requires app-specific password |
On-Premises Exchange | Varies | 587 or 25 | Contact your IT department |
Amazon SES |
| 587 | Uses IAM credentials |
Step-by-Step Configuration
Navigate to Customer Settings > Email Settings
Scroll to the Custom sending addresses section
Click Add new custom sending address
Fill in the required fields:
Email From Address: The address emails will be sent from
Provider: Select "SMTP"
SMTP Host: Your mail server hostname
SMTP Port: The port number (typically 587 for TLS)
SMTP Username: The authentication username
Password: The authentication password
Click Save
Click the envelope icon to send a test email to yourself
Verify the test email arrives and check the email headers to confirm it came from your server
Verifying Configuration
After saving, send a test email by clicking the envelope icon next to the address. The test email:
Is sent to the currently logged-in admin's email address
Uses the configured SMTP settings
Should arrive within 3 minutes if configured correctly
Troubleshooting test emails:
Check your spam/junk folder
Verify SMTP credentials with your IT department
Confirm the SMTP port is not blocked by firewalls
Check that the from address is authorized to send from your mail server
Scope of Custom SMTP Sending
Custom SMTP sending addresses are currently used for:
Email Type | Uses Custom SMTP | Notes |
Email Campaigns | Yes | When campaign's From Address matches a configured address |
Admin Reply Emails | Yes | Replies sent through the email console |
Not in scope for SMTP Sending
The following automated/transactional emails still use PublicInput's default infrastructure:
Email Type | Current From Address |
Meeting Registration Confirmations |
|
Event Reminders |
|
Topic Subscription Confirmations |
|
Security Considerations
SMTP credentials are encrypted at rest using AES encryption
Credentials are never displayed in the UI after initial entry
Only users with Administrator permission can configure sending addresses
Test sends are logged for audit purposes
Troubleshooting
Common Issues
Issue | Possible Cause | Solution |
Test email not received | Incorrect SMTP credentials | Verify username/password with IT |
Test email not received | Port blocked | Try alternate port (587, 465, 25) |
Test email not received | From address not authorized | Ensure the from address is allowed to send from your server |
SSL/TLS errors | Port/encryption mismatch | Use port 587 for STARTTLS, 465 for implicit SSL |
Authentication failed | Wrong credential format | Some servers require full email as username |
Emails marked as spam | Missing SPF/DKIM | Ensure your domain has proper email authentication DNS records |
Checking Email Headers
To verify emails are routing through your SMTP server:
Open a received test email
View the email headers/source (varies by email client)
Look for
Received:headers - they should show your mail server, not SendGrid
Related Features
Custom Email Sending Domains: DNS-based domain authentication for SendGrid (simpler setup, less control)
Email Campaigns: The primary feature that utilizes custom sending addresses
Email Link Tracking: Works with both SendGrid and SMTP-sent emails