FortiGate
FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
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Article Id 191241
Article

Description

SMTP mail delivery problems occur when using BDAT and FortiGate antivirus scanning

Components

  • All FortiGate models running FortiOS 2.80 (MR9 or below)
  • fixed in 2.80 MR10

Steps or Commands

The SMTP BDAT command is an alternative to the DATA command, which can be used when a remote SMTP server presents the CHUNKING verb. CHUNKING is an ESMTP functionality. Microsoft Exchange servers implement this feature by default, as do other SMTP servers.

If BDAT is used to transfer emails between two SMTP servers for which the FortiGate unit is performing antivirus session scanning, delivery problems and/or performance problems may occur caused by retransmission attempts.

The problem occurs when multiple email messages are transfered within the same TCP session using multiple BDAT commands. The transfer of a single email per session, with the use of only one BDAT command does not pose a problem.

This problem will be corrected in a post MR9 maintenance release.

For more information see the related article "FortiGate antivirus and ESMTP mail servers".