What are the main challenges when scaling cold email infrastructure

I’m researching how teams handle cold email infrastructure as their outreach volume grows.

For those who have experience with outbound email systems, what are the biggest challenges when managing multiple sending domains and inboxes?

I’m particularly interested in:

• Maintaining sender reputation

• Managing multiple mailboxes

• Setting reasonable sending limits

• SPF, DKIM, and DMARC configuration

• Monitoring deliverability and bounce rates

What approaches or tools have worked best for you?