Technical contact. The technical contact manages the name servers of a domain name. The functions of a technical contact include assuring conformance of the configurations of the domain name with the requirements of the domain registry, maintaining the domain zone records, and providing continuous functionality of the name servers (that leads to the accessibility of the domain name).
What about the time you clicked on that PayPal link that wasn't really a PayPal link? "Phishing" is a term applied to either websites or emails that pretend to be something they're not in hopes of getting a user to click on something they should have ignored. This tactis is done in hopes of then getting users to provide confidential information they would have otherwise kept to themselves, typically like passwords, financial information, or other personal data. While there are security measure that fight this, the mechanics behind phishing are, unfortunately, also consistently becoming more sophisticated. Even some dedicated antivirus and business-class hosted endpoint protection suites are having trouble keeping up.
One of the most important compatibility factors to consider with email is the mobility question. How often do your employees need to access email via mobile devices? That's an important issue because most email hosting providers deliver some kind of web client usable as a default inbox. Almost all of these can be accessed via a mobile device, so if your employees don't need to access their emails on the road that much, then such mediocre clients are probably fine.