Why do emails go to spam?

Answer: Filters flag messages that look like known spam

Filters flag messages that look like known spam ✓ — Correct! Spam filters compare each message against patterns from known spam, like suspicious keywords, a sender with a bad reputation, or links that have been reported before. When enough of those signs line up, the message gets flagged. False positives do happen, so it's worth checking your spam folder now and then.

Emails arrive too quickly — Wrong. How fast a message arrives isn't what triggers the filter. A legitimate email can land in a second, while a slow one can still be spam. Filters care about what the message looks like and who sent it, not its speed.

Attachments are too large — Wrong. A big attachment might hit a size limit and bounce, but that's a different rule from spam filtering. Filters look at the content and the sender's reputation, not how many megabytes the file is.