Murray S. Kucherawy <msk(_at_)cloudmark(_dot_)com> wrote:
One of the more ubiquitous MTAs out there has a feature called
"connection caching" where it will keep some fixed number of outbound
SMTP connections around, cycled using an LRU method, in case a new
message arrives that is routed to a recent destination to avoid the cost
of making a new connection and doing the initial SMTP negotiation.
I believe Postfix and Exchange can do this.
Our server also does something along these lines. (It's a little more complex
because it ties in to how many simultaneous threads you allow to connect to a
We are doing this as a storage destination queue basis. I think a CS
logic that depends on sitting idle with a presumed server 5 mins usage
imposes a serious problem with receiver loading limits, system
availability and scalability concerns.
For example, if a system allowed for X receivers, the more clients
follow a CS logic, the closer the connections reach X, the more the
server availability goes down.