There’s no single “absolute best” platform for deliverability — it depends on your sending volume, audience, and compliance practices.
If you ask me, I trust Saleshandy and Postmark because they score high for inbox placement. This is because they have a strong infrastructure and deliverability-focused features.
Also, if you want to improve your deliverability, you need a good email warmup tool that sends human-like emails to warm up your account.
Just remember: the platform is only half the battle. A major chunk of deliverability depends on your list quality, sending reputation, and email content.
