Is there a way to filter out anonymous emails?
Assuming that you are using Domino R5 as the SMTP server, go to the Domino public address book, then to the Server / Configurations view. Open the configuration document for this server, then select the tabs Router & SMTP / Restrictions and Controls / SMTP Inbound Controls.
The settings "verify connecting hostname in DNS" and "verify sender's domain in DNS" should do the trick. When you turn these on, Domino will only accept inbound mail from a computer with a known domain name and a sender with a known domain name.
This was first published in October 2001