Pros
The people of AppRiver made AppRiver. Before Zix, people were focused on delivering value to the org and to customers. The culture was supportive, trusting, and fostered innovation. The only good things left about AppRiver are the poor souls still there after the acquisition by Zix.
Cons
Zix purchased AppRiver with a bunch of promises and hasnt delivered on any of them. Zix's culture is based on fear and lack of trust (across the board). They have way too many internal politics for their size which indicates they are completely mismanaged... all the way to the top. There is no single drum beat that the org is marching to, there are many small kingdoms with individual leaders reigning over their minions with fear... fear to keep in line with them, not the rest of the org. They think its normal to pressure teams to deliver on unrealistic goals. They will certainly burn everyone out (at least the ones that stay... many are already leaving).