7.2. Email Anti-Virus

Email Anti-Virus is a service that detects and blocks viruses that invade via Email (SMTP communication).


  • Email-Anti-Virus is used via Service Interconnectivity. You need to apply separately for Service Interconnectivity.

7.2.1. Available Features

You can use the following features in Email-Anti-Virus.
Feature Overview
Virus scan A feature that monitors email (SMTP communication), and executes specified processes when viruses are detected.

7.2.2. Virus Scan Feature

SMTP is the protocol that is targeted for inspection by Email-Anti-Virus.
You can choose the detection and blocking operations. The detection and blocking processes are shown below.
Item Process Information Recorded in Logs
Allow Allows communication. None
Monitors email (SMTP), and detects viruses.
However, traffic is not blocked even though viruses are detected.
Detection Status
Monitors email (SMTP), and detects viruses.
Note that communication is blocked when viruses are detected, and the SMTP Reply Code: 541 is returned to the sender.
Blocking status


  • If NTT Communications judges it necessary, we will notify you via email, etc. of the detection and blocking status (for blocking only).
Routing Settings
Only communication via Email Anti-Virus is targeted for detection. When you use Email Anti-Virus, please set the following routing.
  • The communication addressed to Server Segments targeted for detection is set so that it is routed by vFirewall/Integrated Network Appliance to the Service Interconnect Gateway used for Email Anti-Virus.
  • The communication from the Virtual Machine is set so that it is routed by the Virtual Machine on the Server Segment targeted for detection to the Service Interconnect Gateway used for Email Anti-Virus.
  • If you perform Ping monitoring on the Virtual Machine, you will require an additional Server Segment for direct connection between vFirewall/Integrated Network Appliance and the Virtual Machine.


  • Please do not connect the Server Segments targeted for detection directly to vFirewall/Integrated Network Appliance.
Analysis Capacity
The traffic volume that can be analyzed by Email Anti-Virus is shown below.
Item Performance Remarks
Per service Maximum(5 services used)
Traffic Processing Capacity 200 Mbps 1 Gbps The total value of uplink and downlink.
Number of concurrent sessions 40,000 200,000 The number of sessions that can be connected simultaneously.


  • You can increase the traffic volume up to 1 Gbps, 200,000 sessions (when 5 services used) by applying additional services. When using more than 2 of service, please contact each NTT Communications affiliate beforehand.

7.2.3. Important Points

Used IP Addresses
  • In order to connect the Service Interconnect Gateway with Email Anti-Virus, you must have two IP address blocks available. If the IP address block is already being used, we might ask you to change it.
  • NTT Communications will manage the assigned IP address blocks, and assign IP addresses to the devices that require them.
  • When the actual traffic volume exceeds the contracted traffic volume, the excess traffic might be discarded.
  • The following files are not targeted for detection and blocking.
    • Encrypted files
    • Files set with passwords
    • Files compressed by compression algorithms other than zip/gzip format
    • Files compressed by compression algorithm zip/gzip format three times or more
  • Packets which break TCP/UDP/IP protocol rules or abnormal packets are discarded as a standard function regardless of customer’s configuration.


    • When the IP header is cut off in the middle
    • When the Port number is 0 (zero)
    • When the TCP flag combination is abnormal and others
  • If devices making up this feature are replaced due to malfunction etc., you will not be able to check device logs or event reports from prior to the replacement via the Security Web Portal. In addition, if the regular server and the standby server are switched for a redundantly configured device and they are restored without replacing the device, you cannot check the log or the event reports for the period during which the switching occurred from the Security Web Portal.

  • Email Anti-Virus does not guarantee that the Email Anti-Virus feature has integrity or accuracy, or is suitable for your use. Furthermore, the suitability of the virus identification algorithms provided by the developers or distributors of the devices making up the Email Anti-Virus feature is not guaranteed.

  • The following information might be provided to the developers or distributors of the devices making up the Email Anti-Virus feature.

    • Configuration information obtained from providing Email Anti-Virus
    • Information concerning inspections etc., for Email Anti-Virus
  • We cannot guarantee recovery from failures that might occur due to incompatibility between Email Anti-Virus and your environment, or failures that occur due to your operations other than those specified by NTT Communications.

  • There may be times when the customer’s environment is affected by maintenance services. An advance notice will be sent when there are possible effects to the customer’s environment. This is not applied when we judge the maintenance work urgent to continue service.