IBM Lotus Domino is prone to an overflow condition. The SMTP service fails to properly sanitize user-supplied input resulting in a buffer overflow. With a specially crafted e-mail message containing multiple 'filename' parameters, a remote attacker can potentially execute arbitrary code.
Upgrade to version 8.5.2 FP3 or 8.5.3 or higher, as they have been reported to fix this vulnerability. An upgrade is required as there are no known workarounds.