The Carrier Crow blog https://carriercrow.com/blog Deliverability, A/B testing and list health for newsletter operators. en Wed, 07 Oct 2026 00:00:00 GMT Gmail and Yahoo's bulk sender rules, in plain English https://carriercrow.com/blog/gmail-yahoo-bulk-sender-rules https://carriercrow.com/blog/gmail-yahoo-bulk-sender-rules Wed, 07 Oct 2026 00:00:00 GMT What Gmail and Yahoo have required of bulk senders since February 2024, what breaks if you miss a rule, and how to check your own setup. deliverabilityauthenticationgmailyahoo How long do your subscribers really stay? https://carriercrow.com/blog/how-long-do-subscribers-stay https://carriercrow.com/blog/how-long-do-subscribers-stay Wed, 07 Oct 2026 00:00:00 GMT Averaging how long departed subscribers lasted makes your list look fickle. Survival analysis counts everyone, including the people still here. retentionanalyticssurvival-analysis Is your sponsor's A/B test result real? https://carriercrow.com/blog/is-your-ab-test-result-real https://carriercrow.com/blog/is-your-ab-test-result-real Wed, 07 Oct 2026 00:00:00 GMT Why 4.1% against 3.8% on a few hundred impressions is noise, and how to tell a real difference between two sponsor creatives from luck. sponsorshipab-testingstatistics