Likelihood to Recommend:Not LikelyExtremely Likely
Pros: This is a bullet-proof mail transfer agent used by some of the largest in the email marketing business. It is a mature product with few problems. If you're looking for something that can send 7-9MM+ emails per hour from a single server, this is your ticket. I'm happy that we choose PowerMTA.
Cons: Configuring a server for high throughput is not very easy. This is a software with a learning curve - like many enterprise software solutions - it takes a bit to master. The pricing went way up - for no reason - after the software was acquired by the new owner. The core product has not received many upgrades over the past few years. I'm not saying that patches don't happen. I'm just thinking that the company is no longer making big investments into this mature software. They'll charge you for a developer/test environment license. I'm happy with everything except for the higher cost.
Overall: We used this software to power a multi-million dollar email marketing business.