I'm trying to help someone with an Untangle machine figure out why some of their outbound email is being duplicated. The messages are delivered to the recipient multiple times.
I temporarily replaced their Untangle machine with a pfSense machine for about a month and the issue went away. I put their Untangle machine back in a couple days ago and they've started having problems again.
I'm fairly sure it's some type of timeout issue or a problem with dropped connections while their email is being scanned by Untangle, but I've been having trouble tracking it down.
They have a wireless broadband internet connection. The latency is pretty good, but it has fairly low throughput and a little bit of packet loss here and there. I've tested the hardware they have Untangle installed on fairly thoroughly.
The FAQ suggests increasing timeouts to mitigate lost messages. Is this something that may work for duplicated messages too?
As a test, I'd like to disable anything that may touch their outbound email. They're using the default rack on the open source version of Untangle. Is there anything besides the spam blocker lite, virus blocker lite, and phish blocker lite that I should disable?
I'm also wondering if there are any logs I could look at that might help track down the problem. I'd appreciate any other suggestions as well.