If you are receiving duplicate messages in Outlook or Webmail, this will show what to look for and test to see where the problem resides.
- This can be caused usually by either a malformed message, a bad connection between the client and mail server, or the remote server actually sending it more than once. The first thing is, is this mail seen in webmail being duplicated? If it is, you then need to look in the SMTP logfile and find a few of the connections and see if they are ending properly. In some cases a firewall, AV scanner, or network issue on either side can slow or stop the communication at a certain point which would normally cause the sending server to send the message again. If a proper connection is not closed out then the remote server can think the message did not make it and retry the message.
- It could be a malformed message which is only seen as a client issue as Outlook mostly but other clients as well will "Choke" on the malformed message and kill the download. The download will then start again the next time they try to download mail and they will receive duplicates of everything again up to the malformed message. This can only be stopped by deleting the message in webmail that is causing the problem. There are also filters attached to this ticket that can help prevent these malformed messages by either rejecting or fixing them before they make it to the client.
- The other reason could be caused by a network issue between the client and the server. The fastest and easiest to see if this is the reason is to set up a client on the server directly and see if the issue remains. If it does then it is most likely one of the above causes, if it doesn't then the there is a problem outside of Icewarp on your local or external network that is causing a time out issue with the client or a total connection problem that would show as the same.
Please write support to request these filters if needed.