I mean that one was pretty obvious. Why on earth send a bit.ly link in every email? You have a-hrefs in email, so the link doesn’t even need to be shortened.

> I got some very technical folks on the phone, but all they could say was that everything looked 100% fine and that something we were sending was tripping the spam filters

This “we won’t tell you what triggered it because it helps the spammers” is… questionable, and it feels like security by obscurity. Yes, it may help the spammers a little but not possibly enough to warrant the black hole of debugging legit issues.

The right way to fight spammers isn’t about arms racing with hyper-advanced content filtering. Instead, we need to make it uneconomical.