To switch from another email provider or a self-built mail server to Alibaba Mail, complete the following steps in order.
Procedure

Purchase Alibaba Mail: Purchase the Alibaba Mail service. For details, see Alibaba Mail purchase process.
Create accounts: Set up email accounts for your employees. For details, see Create an employee account.
Migrate email: Move existing emails from your original mailbox to Alibaba Mail. See Email Migration. Skip this step if you do not need to migrate existing emails.
Switch DNS records: Delete or suspend the domain name resolution for your original email service, then add the Alibaba Mail domain name resolution to activate the service. For details, see How to set up DNS records for an Alibaba Cloud (Wanwang) domain name to use Alibaba Mail.