dmaynes wrote:Why would spam filtering cause this kind of random failure? I don't know much about e-mail, but I do not believe that the website e-mail broadcast mechanism attempts to validate e-mail accounts before broadcasting. It might be an interesting question to explore though. That is the only scenario where I would agree that the website admin's e-mail domain might be an issue.
In many cases, spam filtering by the ISP involves several more variables than just the text of the message. Obviously certain text can be considered to be spam ("need help moving 23.6 Million Dollars from Nigeria"). But there are many other factors:
- Similarity to other messages that have been flagged as spam
- Sending a message to a large number of recipients
- Sending from an account different from the sending domain
- Black lists, white lists, and gray lists for sending domain
Typically, the various potential violations are given ratings and weights and so a message ends up with a final score that determines if it is considered spam. Since there are so many factors involved in the rating, and they can even depend on other traffic through your ISP, it can seem somewhat random. It can even be the case that the exact same message gets filtered one day and sent through just fine on another.