Fixed 80% Email Spam Placement
Restored critical transactional and marketing emails to the primary inbox for a fast-growing B2B software startup.
83% of outgoing emails routed to Spam folders at Gmail and corporate servers due to lack of DKIM and bad domain reputation.
All authentication records passing (SPF, DKIM, DMARC alignment), reputation restored to 'High', and 100% inbox delivery.
The Challenge
The client, a B2B SaaS platform, noticed a sudden 80% drop in user sign-up verifications and invoice receipts. Upon auditing, they realized their domain was flagged by Gmail and Microsoft filters, routing almost all outgoing automated messages directly to user spam folders. This caused user sign-up drop-offs and customer support complaints.
Technical Diagnosis
I conducted a raw SMTP header inspection on several test emails and discovered multiple configuration faults:
- The domain had no DKIM signature record published, causing receiving servers to flag email body content as unverifiable.
- Their SPF record was invalid because they had two separate TXT records on their DNS, which violates RFC specifications.
- The IP address of their transactional mail sender (SendGrid) was listed on the Barracuda reputation blocklist.
Steps Taken
- DNS Consolidation: I combined their separate SPF records into a single consolidated string:
v=spf1 include:_spf.google.com include:sendgrid.net ~all, resolving validation errors. - DKIM Key Setup: I generated a 2048-bit DKIM key inside their Google Workspace console and SendGrid dashboard and published them securely to their Cloudflare DNS.
- DMARC Enforcement: I deployed a DMARC policy with email feedback loops (
p=none; rua=mailto:dmarc-reports@domain.com) to monitor aligned traffic. - Blocklist Mitigation: I configured custom reverse DNS (rDNS) pointers for SendGrid and requested IP delisting from Barracuda, which was approved within 12 hours.
Before vs After Results
Within 72 hours of DNS propagation, transactional emails began resolving correctly. Delivery tests showed that SPF, DKIM, and DMARC aligned perfectly. Gmail Postmaster Tools reported their domain reputation increased from 'Bad' to 'High', restoring inbox placement to 100%.
Lessons Learned
Domain reputation is fragile. Never publish multiple SPF records, and always verify DKIM signatures before launching high-volume transactional mailers. Consistently monitor Google Postmaster tools to detect spikes in user-reported spam early.