Recently, we have seen a spike in attacks on Exchange Servers by various financially motivated and state-sponsored attack groups, such as Hafnium. The Remote Code Execution (RCE) vulnerabilities these attackers exploit, such as ProxyLogon, ProxyShell, ProxyOracle, ProxyToken, etc., affect the on-premises Exchange Server 2010, 2013, 2016, and 2019. However, Exchange Online or Office 365 remain unaffected by ‘proxy’ (authentication bypass) attacks and other vulnerabilities.
Due to increasing malicious attacks on Microsoft on-premises Exchange Servers and better security, many organizations are either thinking or already decided to move their email infrastructure to Office 365.
Office365 not only offers protection from malicious attacks, but it also provides secure access to company files and data without using any VPN and from any corner of the world. It’s also highly scalable and does not require hardware or software maintenance.
In this guide, we have discussed methods to migrate mailboxes from on-premises Exchange 2016 to Office365 with minimal downtime and without any data loss.
Methods to Migrate Mailboxes from Exchange 2016 to Office 365
To migrate all mailboxes and mailbox items, such as emails, contacts, attachments, calendar items, etc., from an existing on-premises Exchange 2016 environment to Office 365, administrators can use the following methods,
1. PST Upload Method
In this method, you use the New-MailboxExportRequest PowerShell cmdlet in Exchange Management Shell (EMS) to export the mailboxes from the Exchange database (edb) to PST format. This method is ideal for moving only a few mailboxes from Exchange 2016 to Office 365.
You may also use the Exchange Management Shell to export mailboxes to PST and then import the PST mailboxes to Office 365 accounts. However, this is a long and tedious process where you need to configure several settings in Office 365, map users, and more to upload PSTs. To learn more, refer to this guide on New-MailboxExportRequest.
2. Cutover Migration
Cutover Migration or Express Migration to migrate less than 2000 mailboxes from on-premises Exchange 2003, 2007, 2010, 2013, 2016, and 2019 server to Office 365. The Cutover Migration to migrate Exchange 2016 to Office 365 can be performed via Exchange Admin Center (EAC). Although Cutover Migration is an easier way to migrate multiple mailboxes from on-premise Exchange 2016 to Office 365, it is time-consuming. It may take a few days to weeks to migrate all data based on the number and size of mailboxes and databases. Thus, it is recommended to migrate 150 or fewer mailboxes at a time.
Cutover Migration may also impact the email services as resources will be used by the server machine to process and migrate the mailboxes. For detailed steps, refer to this Microsoft’s step-by-step guide on Cutover Migration.
However, if you need to move or migrate more than 2000 mailboxes, it’s recommended to use an Exchange migration tool as discussed below.
3. Exchange Migration or EDB to PST Converter Tool
Exchange Migration or EDB to PST converter tool, such as Stellar Converter for EDB, can help convert and migrate mailboxes from Exchange 2016 databases to Office 365. Unlike manual methods, as discussed before, the software automates the migration process at up to 4x speeds to save time, avoid downtime, and migrate mailboxes without impacting server resources or performance.
It uses a parallel-processing technique to process and export up to 4 mailboxes from offline Exchange database directly to Office 365. You can also set the priority to export critical mailboxes first to Office 365.
Cloud storage space is expensive, and thus, you don’t want to export unnecessary mail items from user mailboxes to Office 365. The software helps you search, filter, and choose specific mailboxes and mail items you want to export from user mailboxes to Office 365. This saves you from the pre- and post-migration steps of cleaning mailboxes. The software is free to download for evaluation purposes.
Conclusion
Exchange 2016 to Office 365 migration is a tedious process. It requires intensive planning and preparation to migrate the mailboxes and data from Exchange 2016 to Office 365 without halting the email services and productivity. You can use the Cutover Migration method as discussed in this guide to migrate up to 2000 mailboxes from Exchange 2016 to Office 365.
However, if you need to move more mailboxes, the Cutover Migration method may not work. In such cases, you can use a reliable EDB to PST Converter tool as discussed in this post to extract mailboxes from your Exchange 2016 online or offline Exchange database file and export them to PST. You can then manually upload the PSTs to office 365 or use the software to export the mailboxes from the offline Exchange 2016 database directly to Office 365. All you need is admin credentials and permission to import the mailboxes. It’s a much easier, hassle-free, and convenient way that will save your time and avoid downtime while moving mailboxes from on-premises Exchange to Office 365 or another Live Exchange Server.
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