Best SMTP Relay Service Provider for High Deliverability

I’m trying to find the best SMTP relay service provider to ensure reliable email delivery for my needs. I’m particularly focused on high inbox placement, fast sending speed, and minimal bounce rates.

There are many options available, but it’s hard to decide which one actually performs well in real-world use. Can anyone recommend the best SMTP relay service provider based on experience? What features or factors should I consider before choosing one?