Receiving Duplicate Email Because DNS Lookups Are Taking Too Long

  • 7020486
  • 27-Jan-2012
  • 07-Aug-2017


GWAVA 4.5 and Newer


DNS lookups are taking too long (timing out) causing some senders to resend their message, which will cause duplicate messages.


If you are receiving duplicate messages and have found in the GWAVA logs that the DNS lookups (done on RBL and SURBL events) are taking too long or timing out after 10 seconds, then your server may be using mDNS. mDNS  is a service that tries every machine on your network looking for dns info. It is recommended that you turn this off. You can do this by:

1) Using Putty type: vi /etc/host.conf (this will open the host.conf file).

2) Hit the 'Insert' key, this allows you to edit the file.

3) At the bottom of the file type: mdns off

4) Hit the 'Escape" key

5) Type: wq (this will write the changes to the file and quit the file)

6) Reboot the server, type: shutdown -r 0

DNS lookups should be faster now, allowing mail to flow faster which in turn will prevent duplicates from happening.

Additional Information

This article was originally published in the GWAVA knowledgebase as article ID 2032.