The main reason cold outreach emails hit spam after a few weeks usually comes down to three technical configuration issues:

1. Subdomain Alignment: Make sure your SPF and DKIM records explicitly match the sending subdomain you are using, not just the root domain.

2. Sudden Volume Spikes: Jumping from 10 to 50+ emails a day on a new inbox triggers automated inbox provider throttling. You need to step up volume gradually over a few weeks.

3. Tracking Domain Reputation: Using default shared custom tracking links can hurt your sender domain if other users on that shared link send poor-quality copy.

Full disclosure: I build an automated outreach tool (Chronos) focused on domain deliverability and warmup, but fixing those three technical settings manually will solve about 80% of inbox placement drops without buying any new software.

Hope that helps! Let me know if you run into any specific errors on your DNS setup.