Why your invoices and updates might suddenly start going to spam even when nothing else changed.
At KartHost we review email setups for small businesses in the Tomball and Houston area every week. One of the most frequent hidden problems we find is an overloaded SPF record. Over the years companies add services for invoicing, shipping notifications, marketing updates, helpdesk tickets, and more. Each new service adds another “include” to your SPF record until it hits the hard limit and starts breaking deliverability.
Understanding the SPF Lookup Limit
SPF (Sender Policy Framework) tells the world which servers are allowed to send email using your domain name. Every time you add a third-party service it usually requires an “include:” statement. The official SPF standard allows a maximum of 10 DNS lookups during evaluation. Once you go over that limit receiving servers like Gmail, Outlook, and Yahoo treat it as a permanent error. Your legitimate emails can fail authentication and land in spam or get rejected entirely.
This issue builds up quietly. Old SMTP services you no longer use still sit in the record taking up valuable lookups.
Bloated SPF vs Clean SPF Example
Here is a typical bloated record we often see:
v=spf1 include:_spf.google.com include:spf.protection.outlook.com include:sendgrid.net include:amazonses.com include:mailchimp.com include:zendesk.com include:spf.mandrillapp.com ip4:192.0.2.1 include:old-service.com -all
This easily exceeds the 10 lookup limit and causes problems.
A clean, optimized version might look like this:
v=spf1 include:_spf.google.com include:spf.protection.outlook.com ip4:203.0.113.5 -all
Or even better, move heavy services to subdomains (see below).
Common Third-Party Services That Add to SPF
Here are services we frequently see in customer records:
- Google Workspace: include:_spf.google.com
- Microsoft 365: include:spf.protection.outlook.com
- SendGrid, Mailgun, Amazon SES: their respective include statements
- Mailchimp or other marketing tools
- Zendesk, Help Scout, or helpdesk platforms
- Shipping and invoicing tools (ShipStation, QuickBooks, etc.)
- Old SMTP relays or retired services
How to Audit and Clean Up Your SPF
- Find your current SPF record — Use a free tool like MX Toolbox, EasyDMARC, or dmarcian SPF checker. Enter your domain and review the full list.
- List every service you actually use — Go through your accounts and note which ones send email on your behalf. Disable or remove any you no longer need.
- Remove outdated includes — Delete entries for services you stopped using months or years ago.
- Move services to subdomains — This is one of the best long-term fixes. For example, send marketing emails from marketing.yourdomain.com and invoices from billing.yourdomain.com. Each subdomain gets its own clean SPF record.
- Test after changes — Always test with tools like mail-tester.com or GlockApps before sending important batches.
What KartHost Recommends You Do
- Run a full SPF audit at least twice a year
- Keep your main domain SPF record as short as possible
- Use subdomains for any high-volume or third-party sending
- Combine includes where possible and prefer direct IP ranges when practical
- Monitor deliverability with Postmaster tools after cleanup
What We Can Help With
Our KloudEmail and Microsoft 365 customers get SPF reviews as part of regular support. We can audit your current record, identify unused services, clean it up safely, and help set up subdomain strategies when needed.
If you are on a support plan we can:
- Perform a complete SPF and deliverability review
- Remove old services and optimize your records
- Set up subdomain delegation for marketing or transactional email
- Test everything and monitor results
Even if you manage your own email, our local team can guide you through the cleanup or handle it for you.
A bloated SPF record is one of the most common silent killers of email deliverability in 2026. Taking time to clean it up now prevents frustrating spam issues later.
If you suspect your SPF record needs attention, log into the KartHost Customer Center and open a ticket. Our Texas team will review your setup and help get your business emails reaching inboxes reliably again.
We are here to keep your communication flowing smoothly.
