The biggest factors that affect deliverability are list quality, sender reputation, authentication setup, and engagement signals. High bounce rates, spam complaints, and sending to unengaged contacts lower reputation. Proper SPF, DKIM, and DMARC configuration improves trust with mailbox providers. Consistent engagement, especially clicks, strengthens inbox placement over time.

To improve inbox placement, focus on three areas: clean your list, authenticate your domain correctly, and send to engaged segments first. Use validation tools to remove invalid emails and likely complainers. Monitor sender reputation through tools like Google Postmaster. Test inbox placement across providers because placement can vary between Gmail, Outlook, and Yahoo.

Open rates are useful for identifying trends but should not be your primary performance metric. Privacy updates, such as Apple Mail Privacy Protection, can inflate open rates. Clicks and downstream actions are stronger indicators of engagement. If open rates suddenly drop significantly, it may signal a deliverability issue.

In B2B marketing, segmentation should be based on engagement, behavior, and recency. Create lists based on recent opens or clicks, content downloads, page views, and lifecycle stage. Avoid sending to large unengaged segments. Sending to active contacts first helps generate positive engagement signals and protects sender reputation.