Email queue service for .NET

We're building an app that sends email using our clients' servers. The servers have different settings in regards to how many emails can be sent per connection/per second/etc.

Can someone recommend a component for this so we don't have to build our own? I came across MailBee Message Queue (http://www.afterlogic.com/products/message-queue)开发者_如何学Go, but I'd love to be able to compare it against something (or hear your experiences with it).

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I've used other products from Quiksoft before and found them to be good. They appear to have an express SMTP server product.