Many people these days rely on web mail for their emails. This leaves all your emails on the servers of your providers and you are dependent on their safety and security for the storage and archiving of your emails. A safer way is to collect and store your emails on your machine using an email client. Offices tend to use Outlook which is part of Microsoft's expensive Office suite and in the past individuals have used Outlook Express which is now no longer supported.
Thunderbird email client is from the same stable as Firefox and is a good replacement for your proprietary email clients. If you need calendars attached then Lightning can be downloaded as an extension through the Tools menu.