Then EVERYONE stopped because it's awful. Modern ISPs don't like SMTP floating around, (DKIM, DMARC, SPF) are a pain to maintain over time, exploits will happen, and your free off-the-shelf virus and spam filters suck compared to the big companies seeing billions of messages per day.
Then EVERYONE stopped because it's awful. Modern ISPs don't like SMTP floating around, (DKIM, DMARC, SPF) are a pain to maintain over time, exploits will happen, and your free off-the-shelf virus and spam filters suck compared to the big companies seeing billions of messages per day.