When using Google Workspace with multiple domains, SPF alignment becomes problematic for alias domains because Google's servers ultimately send emails using your primary domain's infrastructure. While DKIM can be properly configured for aliases through additional signatures, SPF presents unique challenges since it validates the actual sending server's IP against the domain in the Return-Path address.

Google's SMTP servers will always use your primary domain in the Return-Path (envelope-from) header, which causes SPF alignment failures when recipients check DMARC for your alias domain. This creates a security gap where legitimate emails from your alias might fail authentication checks.

While there's no perfect solution within Google Workspace's native configuration, these approaches can help:

// Example SPF record for aliasdomain.com
"v=spf1 include:_spf.google.com ~all"

Combine this with DKIM signing for your alias domain (configured in Google Admin Console) to achieve partial alignment. The most reliable method is to implement these additional measures:

For mission-critical alias domains, consider these enterprise solutions:

// Alternative SPF record using redirect
"v=spf1 redirect=primarydomain.com"

Or implement a more complex setup using subdomain delegation:

// DNS configuration for mail.aliasdomain.com
mail IN CNAME ghs.googlehosted.com.
"v=spf1 include:mail.aliasdomain.com -all"

After implementation, use these tools to verify your configuration:

• MXToolbox SPF Validator
• Google Admin Toolbox Check MX
• DMARC analyzer tools like dmarcian or ValiMail

Remember that while these solutions improve deliverability, they don't provide perfect SPF alignment in the strictest DMARC sense. The ultimate solution might require routing alias domain emails through different infrastructure.

When using Google Workspace with multiple domains (primarydomain.com as primary and aliasdomain.com as alias), email authentication becomes tricky. The SPF (Sender Policy Framework) record for aliasdomain.com will always show a misalignment because Google's servers technically send from the primary domain's infrastructure.

Here's what happens during email transmission:

From: user@aliasdomain.com
Return-Path: bounce-primarydomain.com
Received-SPF: pass (google.com: domain of bounce-primarydomain.com)

The SPF check passes for the primary domain but fails alignment for the alias domain.

Option 1: SMTP Relay Configuration
Configure Google Workspace to use a custom SMTP relay for the alias domain:

# Example Postfix configuration for relayhost
relayhost = [smtp-relay.gmail.com]:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_tls_security_level = encrypt

Option 2: Dual SPF Records
Create separate SPF records while maintaining Google's requirements:

; aliasdomain.com TXT record
"v=spf1 include:_spf.google.com include:primarydomain.com ~all"

; primarydomain.com TXT record  
"v=spf1 include:_spf.google.com -all"

For full email authentication, your DMARC policy should account for both SPF and DKIM:

; DMARC record for aliasdomain.com
"v=DMARC1; p=none; rua=mailto:dmarc@aliasdomain.com; 
sp=none; adkim=r; aspf=r"

The aspf=r parameter indicates relaxed SPF alignment.

For developers comfortable with API integration, you can implement custom routing:

// Sample Gmail API snippet for custom envelope sender
const {google} = require('googleapis');

async function sendWithCustomEnvelope() {
  const gmail = google.gmail({version: 'v1', auth});
  const res = await gmail.users.messages.send({
    userId: 'me',
    requestBody: {
      raw: createMessage(
        'user@aliasdomain.com',
        'recipient@example.com',
        'Subject',
        'Message body',
        'bounce-aliasdomain.com' // Custom return path
      )
    }
  });
}

After implementation, verify your configuration with:

dig TXT aliasdomain.com +short
dig TXT _dmarc.aliasdomain.com +short
telnet gmail-smtp-in.l.google.com 25

Use tools like MXToolbox or Google's Admin Toolbox to test email authentication.