22% of our emails went to spam.

In February we noticed trial-to-paid conversion had dropped from 14% to 9% with no product changes. We spent two weeks looking at the product before someone suggested checking email deliverability.

We ran a seed test across Gmail, Outlook, and Yahoo. Results:

• Gmail (personal): 94% inbox

• Gmail (custom domain): 61% inbox

• Outlook: 78% inbox

• Yahoo: 88% inbox

The custom domain Gmail number was the killer. A large chunk of our B2B users were on Google Workspace with a custom domain. Our onboarding emails, trial expiry warnings, and password resets were landing in spam for nearly 40% of them.

Root cause: we had switched sending providers in December and never set up SPF, DKIM, and DMARC records for the new provider. We had been sending authenticated mail through the old provider and unauthenticated mail through the new one for 10 weeks.

Fix took 3 days: DNS records, a subdomain dedicated to transactional mail, and a warmup period. Conversion recovered to 13% within 3 weeks.

When did you last actually test where your emails land?