How are you handling cold email infrastructure once you have multiple domains?

I've been looking more seriously at the infrastructure side of cold email and this is the part that gets annoying pretty quickly.

With one domain and a couple of inboxes, it's pretty easy to keep track of everything. Once you start using multiple domains and more mailboxes, there are a lot more things to keep an eye on. DNS, SPF, DKIM, DMARC, sending limits, mailbox health, domain reputation and making sure everything is connected properly.

The actual sending isn't really the difficult part. It's keeping the whole setup organized without spending half your time managing inboxes.

I've also seen completely different opinions on how many mailboxes people should have on one domain. Some people keep it very low, while others seem comfortable running more then there's the question of what to do when a mailbox starts having deliverability problems.

I'm at the point where I'm trying to figure out whether it's better to manage all of this yourself or use an infrastructure provider and spend more time on the campaigns themselves.

Would be useful to hear how people who are already running cold email at scale have set this up.