The use of POP (or Imap) email was and still is widespread, we have just completed a full migration from an older Outlook collecting POP email to a new mail server hosted on the clients site. Negates the issues of any internet connection problems stopping access as its not hosted in the cloud.
We migrated at least 7 years of emails in to the system (around 70000 or more emails) so they have all the history, no problems found, some time to allow the desktops to synchronize (a few days).
Client now has Outlook, Webmail (anywhere with internet) and ActiveSync for the mobile devices (such as phones and tablets). Adding to the features are shared calendars, shared mail folders, document storage, notes tasks and voice recordings all available from the web client.
To complete the installation its all branded with the clients corporate logo.