We are in the process of deciding whether to replace LSMTP with HDMAIL or use another mailer. We currently run Listserv(tm) under windows with LSMTP.

Looking at our hourly delivery between 45,000-75,000 messages/hour and the size of our mail queue which is frequently over 150,000, I am not sure whether the "standard" Linux mail transports are a reasonable replacement. My main worry is the queue size. Even EXIM does not recommend queues over 50,000.

As far as a Windows-based mail transport, I see that Microsoft Exchange 2007 Edge Transport server is suggested to handle 20 deliveries/second (72,000/hour) and process a queue of up to 200,000 items. Does anyone have experience with this product?