Exchange support sites providing helpful information.
How to Export information:

<ul><li><a href="http://support.microsoft.com/kb/290859" target="_blank">How to Export Data using an Outlook Email Client</a></li><li><a href="https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer?esab=a&amp;s=export+data+from+thunderbird&amp;r=0&amp;as=s" target="_blank">How to Export Data from Mozilla Thunderbird</a></li><li><a href="https://support.google.com/mail/answer/24911?hl=en" target="_blank">How to Export Contacts from Gmail</a></li><li><a href="https://support.google.com/calendar/answer/37111?hl=en" target="_blank">How to Export Calendar Data from Gmail</a></li><li><a href="https://support.google.com/a/answer/100458?hl=en" target="_blank">How to Migrate Data Away from G Suite</a></li></ul>

How to Import information using Microsoft&#39;s tools:

<ul><li><a href="https://support.office.com/en-us/article/Import-and-export-Outlook-email-contacts-and-calendar-92577192-3881-4502-b79d-c3bbada6c8ef" target="_blank">Import Email, Contacts, and Other Data Into Your Account</a></li><li><a href="https://support.office.com/en-us/article/import-contacts-to-Outlook-bb796340-b58a-46c1-90c7-b549b8f3c5f8" target="_blank">Import Contacts Using Outlook 2013</a></li><li><a href="https://support.office.com/en-us/article/import-contacts-to-Outlook-bb796340-b58a-46c1-90c7-b549b8f3c5f8#ID0EAACAAA=Office_2010" target="_blank">Import Contacts</a> (Designed for Outlook 2010)</li><li><a href="http://office.microsoft.com/en-us/mac-outlook-help/import-information-into-outlook-HA102928320.aspx?CTT=5&amp;origin=HA103451643" target="_blank">Import Information Into Outlook</a> (Designed for Outlook 2011)</li><li><a href="https://support.office.com/en-us/article/import-contacts-to-Outlook-bb796340-b58a-46c1-90c7-b549b8f3c5f8#ID0EAACAAA=Outlook_on_the_web" target="_blank">Import Contacts Using Outlook Web App</a></li></ul>

You can import your contacts, calendar events, and email messages into your Exchange mailbox. The basic idea is that you export data from your existing email client or service, then import it using one of Microsoft's tools.

Exchange Setup: How to Import Data into Exchange