When debugging email delivery issues between Namecheap's mail servers and Gmail, you might encounter this frustrating SPF softfail message:

Received-SPF: softfail (google.com: domain of transitioning xx@mydomain 
does not designate ... as permitted sender)

Your existing TXT record:

v=spf1 mx include:mailgun.org ~all

This configuration works for Mailgun but fails for Namecheap's servers because:

• Namecheap uses private MX records not visible in your DNS zone
• The mx mechanism only checks visible MX records
• Namecheap's infrastructure uses different IP ranges than what's covered by your SPF

For Namecheap's Private Email service, you need to:

v=spf1 include:mailgun.org include:spf.privateemail.com ~all

Or if you want to be more specific with IP ranges:

v=spf1 ip4:77.77.77.0/24 ip4:88.88.88.0/24 include:mailgun.org ~all

After updating your SPF record:

1. Wait for DNS propagation (up to 48 hours)
2. Send test emails to Gmail
3. Check headers using Gmail's "Show original" option

Example of successful verification:

Received-SPF: pass (google.com: domain of contact@yourdomain.com 
designates 77.77.77.1 as permitted sender)

Avoid these mistakes:

• Using both mx and include:spf.privateemail.com (redundant)
• Not including all sending services (limit of 10 DNS lookups)
• Using ?all instead of ~all for testing

For advanced configurations with multiple providers:

v=spf1 include:mailgun.org include:spf.privateemail.com 
include:_spf.salesforce.com -all

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When integrating multiple email providers (Mailgun + Namecheap Private Mail), I hit a peculiar SPF validation issue where Gmail flagged Namecheap-originating emails with:

Received-SPF: softfail (google.com: domain of transitioning xx@mydomain 
does not designate [IP] as permitted sender)

My initial SPF record looked clean:

v=spf1 mx include:mailgun.org ~all

But Namecheap's architecture complicates things. Unlike traditional MX setups:

1. Their mail servers use hidden MX records not visible in your DNS zone
2. Outbound IPs aren't included in standard SPF validation paths

After testing multiple configurations, this SPF record resolved the issue:

v=spf1 ip4:198.54.117.0/24 ip4:185.92.72.0/22 include:mailgun.org ~all

Key elements:

• Namecheap's documented IP ranges for their private mail service
• Maintained Mailgun integration via include
• Kept softfail (~) for non-critical domains

Use these to validate your SPF setup:

# Command line check
dig TXT yourdomain.com +short

# Online validators:
- MXToolbox SPF Checker
- Google Admin Toolbox

Remember: DNS changes may take up to 48 hours to propagate globally.

Add this DMARC record for analytics:

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

This helps track which providers are properly authenticating your emails.