Lotus Domino SMTP server 4.63 through 5.08 allows remote attackers to cause a denial of service (CPU consumption) by forging an email message with the sender as bounce@[127.0.0.1] (localhost), which causes Domino to enter a mail loop.
https://exchange.xforce.ibmcloud.com/vulnerabilities/7012
https://euvd.enisa.europa.eu/vulnerability/EUVD-2000-1188
http://www.securityfocus.com/bid/3212