On 7/10/20 14:36, Job Cacka via mailop wrote:
There is PAT firewall that load balances multiple networks.
This is a possibility, especially if the load-balancing is pushing some incoming traffic to the wrong internal network.
A Barracuda spam filter
If this is configured to drop traffic based on originating IP, it could be the problem, especially if it's using blacklists that change rapidly or if it is configured to deny connections when it can't successfully phone home to evaluate them.
And then the MX server.
This is doubtful as the Barracuda is what is opening the socket based on the banner on Adam's test.
It was working well until about 6-8 weeks ago when we began to notice the intermittent issue.
What configuration changes were made around that time? -- Jay Hennigan - j...@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV _______________________________________________ mailop mailing list mailop@mailop.org https://chilli.nosignal.org/cgi-bin/mailman/listinfo/mailop
