How to optimize “Unibox” and send bulk emails without affecting the open rate in Smartlead?

Hello everyone,
I am using Smartlead for a large email campaign and have encountered a few problems as Steal Brainrot Game follows:

I see “Unibox” (central mailbox) and many email sending accounts, but the open rate does not increase as expected.

I have configured SPF, DKIM, and DMARC, but many emails still fall into spam or promotion folders.

I want to find a way to:

Minimize the number of emails being marked as spam when using multiple sending accounts.

Keep a good open rate when using bulk sending + automatic follow‑up.

Create a workflow that is suitable for the trend in 2025 (like AI, deeper personalization).

If anyone has done this well on Smartlead or has a specific scenario, please show me a sample or share your experience. Thank you very much!