SMTP content filter engines, including (1) GFI MailSecurity for Exchange/SMTP before 7.2, (2) InterScan VirusWall before 3.52 build 1494, (3) the default configuration of MIMEDefang before 2.21, and possibly other products, do not detect fragmented emails as defined in RFC2046 ("Message Fragmentation and Reassembly") and supported in such products as Outlook Express, which allows remote attackers to bypass content filtering, including virus checking, via fragmented emails of the message/partial content type.

NAI WebShield SMTP 4.5 and possibly 4.5 MR1a does not filter improperly MIME encoded email attachments, which could allow remote attackers to bypass filtering and possibly execute arbitrary code in email clients that process the invalid attachments.

McAfee WebShield SMTP 4.5 allows remote attackers to cause a denial of service via a malformed recipient field.

McAfee WebShield SMTP 4.5 allows remote attackers to bypass email content filtering rules by including Extended ASCII characters in name of the attachment.

WebShield SMTP 4.5 allows remote attackers to cause a denial of service by sending e-mail with a From: address that has a . (period) at the end, which causes WebShield to continuously send itself copies of the e-mail.