Fix Question Marks for Non-Google Email Clients

Written By Matt Sywulak

Last updated 27 days ago

What You Need to Know

When Google Workspace users send email to other internal users using third-party email clients (Microsoft Outlook, Canary, Superhuman, etc.), recipients may see a question mark next to the sender's name in Gmail's web interface. This happens because Google can't verify the sender's IP address against your SPF record.

You can fix this by adding authorized IP addresses to your SPF record using a scalable approach that avoids SPF lookup limits.

Why This Happens

Google Workspace expects internal email to come from Google's mail servers. When someone uses Outlook or another external client, the email routes through that client's servers with the sender's home or office IP address. Gmail sees an unfamiliar IP address and displays a question mark to warn the recipient.

This only affects internal email (your users emailing each other). External recipients don't see these warnings because Google’s mail servers use different validation rules for externally destine messages.

When You Need This Fix

Apply this solution if your organization has users who:

  • Use Microsoft Outlook with Google Workspace accounts

  • Use alternative email clients like Canary, Superhuman, Mailbird, etc.

  • Send email from home offices or remote locations

  • Frequently see question mark warnings on internal emails

If everyone uses Gmail's web interface or Google's mobile apps exclusively, you don't need this configuration.

Understanding SPF Limits

Before adding IP addresses to your SPF record, understand these constraints:

String length: Each DNS TXT record is limited to 255 characters per string, with a practical limit of ~512 characters total for the entire record.

DNS lookup budget: SPF allows a maximum of 10 DNS queries. Each include:, a:, mx:, ptr:, and exists: mechanism counts as one lookup. Exceeding this limit causes SPF validation to fail.

The solution: Rather than listing every IP address directly in your SPF record (which quickly exceeds length limits), you create individual DNS records for each IP and use a single exists: mechanism to reference them all.

Add Remote User IP Addresses

Step 1: Create DNS Records for Each IP Address

For each remote user or office location, create a new DNS A record in your domain's DNS management portal:

Host/Name:

192.168.1.100._spf.clients.yourdomain.com

Replace 192.168.1.100 with the actual IP address (use periods, not dashes) and yourdomain.com with your actual domain.

Points to:

127.0.0.2

This is a marker IP that indicates an SPF-authorized address. It's not used for actual mail routing.

Example: If your remote user sends from IP address 203.0.113.45, create:

  • Host: 203.0.113.45._spf.clients.example.com

  • Points to: 127.0.0.2

Repeat this for each remote IP address you need to authorize.

Step 2: Update Your SPF Record

Add the exists mechanism to your domain's SPF record. This single entry covers all the individual IP records you created:

If your current SPF record looks like this:

v=spf1 include:_spf.google.com exists:%{i}._spf.inkyphishfence.com ~all

Update it to:

v=spf1 include:_spf.google.com exists:%{i}._spf.inkyphishfence.com exists:%{i}._spf.clients.yourdomain.com ~all

Replace yourdomain.com with your actual domain name.

Step 3: Test the Configuration

After adding the DNS records and updating your SPF record:

  1. Wait 10-15 minutes for DNS propagation

  2. Have the remote user send a test email to an internal recipient

  3. Check if the question mark still appears in Gmail's web interface

  4. If the warning persists, verify the DNS records with a tool like nslookup or dig

Benefits of This Approach

Scalable: Add hundreds of IP addresses without hitting SPF lookup limits. Each individual IP record doesn't count against the 10-lookup maximum—only the single exists mechanism does.

Manageable: Add or remove authorized IPs by creating or deleting individual DNS records. No need to edit your main SPF record each time.

Secure: IP addresses are "obfuscated" in DNS rather than listed directly in your SPF record, making it harder for attackers to enumerate your authorized sending locations.

Common Issues

Question Mark Still Appears

Cause: The DNS record may not have propagated, or the IP address might be incorrect.

Solution: Verify the user's current sending IP address by checking email headers. Ensure you created the DNS record with the correct IP format (periods, not dashes).

SPF Validation Failures

Cause: Syntax error in the SPF record or DNS A record.

Solution: Use an SPF validator tool to check your record. Ensure the exists mechanism references the correct subdomain (_spf.clients.yourdomain.com).

Dynamic IP Addresses

Cause: Remote users on residential internet often have IP addresses that change periodically.

Solution: This approach works best for static IP addresses. For users with dynamic IPs, consider requiring VPN access or encouraging use of Gmail's web interface or mobile apps.