That's sort of how Gmail does work in my experience. Once there is evidence of an account replying to email from a "less reputable" domain / IP, they tend to le

That's sort of how Gmail does work in my experience. Once there is evidence of an account replying to email from a "less reputable" domain / IP, they tend to let all follow-up correspondence through. The problem is that people managing their own server wouldn't be able to initiate conversations with people who give them business cards, for example.