A follow up to many of the problems we have been experiencing with Smartermail Gateways.
We have been using Smartermail Gateways as both Incoming *AND* Outgoing Gateways to our Smartermail Enterprise server. The reason we had this configuration was to offload Spam & Antivirus checks on both Incoming and Outgoing email to another server(s). As we used Declude and HijackThis, which are both CPU and Memory intensive, at the time we felt this seemed like a smart move...and it worked relatively well with the exceptions I noted in my posts in this thread.
Recently, after upgrading to Smartermail v14, we had the need to stop using our Smartermail Gateways for Outgoing (having to do with one of our hosted domains being a split domain that has email hosted both at Google Apps and on our Smartermail Enterprise server), and use our Smartermail Gateways only for Incoming . In the two days since almost all of our problems that we had experienced when using Smartermail Gateways cleared up.
The moral of this cautionary tale is that Smartermail Gateways work great as *EITHER* an Outgoing Gateway or an Incoming Gateway, but things may begin to work not as intended when you try using Smartermail Gateways as both.