After nearly a decade helping companies navigate these changes, Rubin shares insights with Apollo.io on key mistakes that consistently hurt cold email campaigns. Email providers are suspicious of domains that suddenly start sending hundreds of emails with no history. Mistake #4: Spiking send volume instead of ramping graduallyHere’s a common scenario: The quarter’s ending, targets loom large, so the sales team decides to crank up email volume — doubling or tripling daily sends overnight. Email providers prefer gradual, predictable increases that look like natural business growth rather than aggressive scaling that resembles spam operations. The difference is they understand that email deliverability is a technical discipline requiring proper setup, monitoring, and maintenance.