Summary
Emails to certain domains are rejected by the recipients' mail servers in ISVW. One of the following errors occurs after the HELO command:
501 Syntax error
220
HELO isvw.illegal_character.com
501 Syntax error in parameters or arguments
HELO isvw.illegal_character.com
501 Syntax error in parameters or arguments
The issue occurs due to a syntax error in the HELO command caused by an invalid character in the hostname.
By default, ISVW uses the machine's hostname in the SMTP HELO command. In the example above, the hostname contains an underscore ( _ ), a character that is not allowed in the fully qualified domain name (FQDN). Some mail servers treat such HELO commands as a syntax error and reject the SMTP connection. For more information about the allowed characters in FQDN, refer to this IETF document: Domain Names – Implementation and Specification.
Host not found
Helo command rejected: Host not found
This error occurs because ISVW uses the computer name of the operating system as the server name for the SMTP connection.
Details
To resolve the issue, set a valid domain hostname:
- Back up the intscan.ini file:
- Windows: C:\Program Files (x86)\Trend Micro\InterScan VirusWall\intscan.ini
- Linux: /opt/trend/isvw6/intscan.ini
- Open it with Notepad.
- Look for “DomainHostName” and change its value to a legitimate FQDN. For example:
DomainHostName=isvw.mydomain.com
- Save the changes.
- Restart the InterScan VirusWall service.
If the issue persists, refer to this information from Microsoft TechNet for checking DNS server issues: 450 4.7.1 Client host rejected: cannot find your hostname, [xxx.xxx.xxx.xxx]
