There are not many enterprise level ESPs that improve their platform at the rate that Adestra does. Many ESPs seem to collect a big group of major clients and then sit on their eggs, while their technology grows old and outdated. I've been an Adestra client for over two years and use the platform heavily. The best part about the platform is that they are constantly releasing major new features to keep up with their clients' needs. Not only are they constantly developing cool, new stuff, but they really listen to your input. I've asked for at least 5 updates/enhancements and every single one of them has been implemented in less than 12 months. After 15+ years, the platform is incredibly feature rich and suited well for the most demanding email markers.
The segmentation/filter tool is slightly difficult to use, although it has many advantages once you get used to it. The message workflow also has a learning curve, but it's very smooth once you get used to it (this goes for any enterprise-level application).
The flexibility of the account structure is incredibly advantageous and unique among ESPs. Whether you are presetting templates, domains, from addresses, lists, IP addresses, footers, unsubscribe lists, databases, or even completely separate client accounts/brands, Adestra gives you an incredible amount of flexibility in how you setup and configure your account.
The support is top notch. The chat window is not just a sales pitch — it's always manned with intelligent, english-speaking representatives who are ready to help, and will actually resolve your issue.
The reporting section is very powerful, especially the geo-targeting, heatmap, social, device, conversion, and form reporting. They also have excellent list-based reporting which is lacking in many platforms.
The automation program builder is extremely useful, although it certainly has a learning curve. The form builder is really powerful and flexible. They also offer a variety of message editors (WYSIWYG, Drag and Drop, Module Based, HTML code) to suit every type of user, which is really unique.