Apollo is shit when comes to deliverability. It's not just about the tool, deliverability depends on various factors like what's your ESP (Email service provider), your lead hygiene, and copy obviously. Domain reputation/age/blacklisting, warmup score, mailbox performance across campaigns also adds to the overall deliverability score.
If you need help figure out what's wrong with your existing setup, feel free to DM and I'll guide you in the right direction.
