Open Relays and Mail Sinks

Email is a “store and forward” protocol. The sender doesn’t connect directly to the recipient to send the mail with just one network hop, rather the sender connects to a mailserver (usually referred to as an “MTA”, short for Mail Transfer Agent) and sends the message there. Once that MTA has received the message it sends it on to another MTA, and so on until it...

I need IP addresses to handle the volume

Number two of seven in our occasional series on why ESPs need, or don’t need, lots of IP addresses to send mail properly. I need lots of IP addresses so my MTAs can handle the volume of mail sent Why this is right One IP address per outbound smarthost is a sensible minimum. It is possible to set up multiple smarthosts behind a single IP address using a proxy server or reverse load balancer, and...

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