I would be very happy to recommend Adestra for your email marketing partner. The experience we at the IET have had with Adestra has been consistently excellent throughout the 8 years that we have worked with them.
The Messagefocus tool itself is extremely user friendly and yet has all the functionalities that one would expect from a top class email service provider.
The Support network they offer is also very impressive, both from the online live chat portal or the phone service during working hours. The turnaround for sorting issues that arise is always extremely quick.
So for all of the above reasons and from everything I have experienced in my time managing the account relationship with them, I would strongly recommend them.