One important aspect of getting good delivery is to look like legitimate email. A big part of that is to not do what spammers do. More specifically, do not do the things that ISPs trigger on when identifying spammers.
There are a lot of these “tricks” and “delivery techniques” used by spammers. They may seem like tiny things, but these are things that any legitimate mailer will want to avoid doing in order to get the best delivery you can.
When I notice an otherwise legitimate mailer doing something “that spammers do” or a spammer doing something that makes me think “don’t do that” I’ll talk about it here.
Keep an eye open for posts tagged “TWSD” (that’s what spammers do!).