We send a moderately decent amount of legitimate mail to our subscribers (about 400K opt-in newsletter members) using Postfix. We get excellent inbox deliverability percentages, because we use the latest version of Postfix with settings we've arrived at with the help of many on this list, are on the major whitelists and feedback loops, etc.
Now, we want to turn our focus to delivery speed. We use a local resolver (Unbound), which seems to have sped things up a bit. We also use Postscreen, so our SMTP processes are busy sending mail, instead of dealing with bots. We use a fallback relay to re-attempt deliveries that don't go the first time from our primary server. But it still takes the better part of a day to send all the mails out. We'd like to shrink that time as much as (reasonably) possible. I know nothing about Postfix optimization, and therefore have no idea where to even start. Are there any tools that anyone can recommend to help us track down where our limiting factors are when it comes to mail delivery? At this point, we don't know if it's CPU, memory, disk access speed (which is what I suspect), or something else altogether. We don't even know how to measure how many messages are being delivered on average every second/minute/hour, etc. so that we can start with a baseline to measure improvements. I'm sure many have been down this road before - care to shove a n00b in the right direction? Thanks, SteveJ
