After that date, Microsoft will no longer provide:
Technical support for problems that may occur
Bug fixes for issues that are discovered and that may impact the stability and usability of the server
Security fixes for vulnerabilities that are discovered and that may make the server vulnerable to security breaches
Time zone updates
Exchange Server 2013 will continue to run after this date, of course; however, due to the risks listed above, we strongly recommend that you migrate from Exchange Server 2013 as soon as possible. If you haven't started your migration from Exchange Server 2013 to Exchange Online or Exchange Server 2019, get going now!
If you're migrating to Exchange Online, you might be eligible to use our Microsoft FastTrack service. FastTrack provides best practices, tools, and resources to make your migration to Exchange Online as seamless as possible. Best of all, you'll have a support engineer walk you through from planning and design to migrating your last mailbox. For more information about FastTrack, seeMicrosoft FastTrack.