Outbound SMTP is blocked by SonicWall
Posted on 2015-02-12
Having a strange problem. We have a SonicWall TZ200 with WAN failover set up between Comcast and AT&T DSL. The SonicWall is blocking outbound SMTP traffic on port 25 but only when both Internet connections are connected. If I disconnect either connection, the traffic goes out. As soon as I connect both, SMTP traffic is blocked but everything else goes out. There are not access rules set up from LAN to WAN except for the default rule that allows all traffic. I know it's the SonicWall because it works when I connect a computer directly to Comcast or DSL. The other strange thing is that we had a T1 connected prior to upgrading to Comcast and it worked fine. Scratching my head on this one. Any ideas?