Hi everyone,

About 18 hours ago I moved my SmarterMail installation to a new Windows Server 2025 machine. I also changed provider, so the server now sends from new IP addresses, and I’m in the middle of warming them up.

I expect Microsoft and Yahoo to apply their usual preventive blocks any time now. Fortunately, routing rules let me match on the recipient domain and relay those messages through a gateway whose IP already has a good reputation, so those cases are covered.

The first issue came from an Italian provider (Italiaonline: libero.it, virgilio.it, etc.). They haven’t blocked me, but they treat the new IP as suspicious and ask me to slow down:

RSP: 451 too many messages, slow down. [smtp-23.iol.local; LIB_650]

They seem to expect the volume from a new IP to grow gradually. If I route all their traffic through the gateway, the new IP never builds any reputation with them and I never get out of this. What I need is to keep sending directly, but at a controlled pace.

This made me think of Postfix, which can throttle per destination domain (concurrency and rate). Something similar in SmarterMail would be very useful: for example, a maximum number of messages per hour, or of simultaneous connections, to a specific destination domain. It would make IP warm-ups much easier to manage.

For now I’ve set up a routing rule that sends mail from some sender domains through the gateway and lets the others try direct delivery. It works, but it’s a workaround.

A second suggestion, about the spool: today I can select messages in “Waiting to Deliver” and force delivery. It would help to also be able to send selected messages through a gateway, without having to create a routing rule first. I think this would be useful in many situations: a provider temporarily deferring your IP, an urgent message stuck in the queue, a quick test of a gateway, and so on.

What do you think? Has anyone found a better way to handle warm-ups with SmarterMail?