Document information

Document ID: 4626
Subject: Specifying fully qualified domain name ( FQDN ) for SMTP communication
Creation date: 12/14/15 4:35 PM
Last modified on: 4/13/22 10:37 AM

Specifying fully qualified domain name for SMTP communication

Many SMTP servers on the Internet require a fully qualified domain name in the HELO/EHLO command for SMTP. Xeams tries to get the fully qualified domain name from your operating system. However, often the OS only returns the current host name rather than FQDN.

Use the following method to manually specify a FQDN in the HELO/EHLO command of SMTP, which will force the SMTP server to ignore the value returned from your OS.

Instructions for Xeams build number 5383 and newer

  • Log in to Admin Console using the 'admin' account
  • Click Server Configuration on the main menu
  • Select Advanced Configuration tab
  • Specify a domain name for SMTP HELO domain and Smtp Signature.
  • Click Save

Instructions for Xeams build number 5382 and earlier

  • Using Windows Explorer, or the terminal window on Linux/UNIX, go to the config folder in Xeams installation directory.
  • Look for a file called in this folder. If it does not exist, create one using any text editor such as Notepad on Windows and VI on Linux/UNIX. IMPORTANT: File names are case-sensitive on Linux/UNIX. For compatibility reasons, we recommend you use all lower case letters for this file name even on Windows.
  • Enter the following line:


    For example:

  • Save the file
  • Restart Xeams

What value should I use for FQDN?

You should use a domain name that exists for your PTR record in the DNS. Here are the steps to find this domain name.

  • Visit from the same machine where you have installed Xeams.
  • Besides showing your IP address, this website will also display the domain name for Reverse Lookup
  • This is what you should use as the FQDN
IMPORTANT: If no reverse lookup value is found, you should ask your ISP to add a PTR record for your IP address. Most email servers will reject your email if a PTR record is not found.

User comments

Posted by Rob on 7/28/15 3:41 PM

This seems to be broken in 4.8 build 5792. Putting anything in the SMTP Helo Domain has no effect when issuing the helo command in an SMTP session.

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