Email is a traditional but still important global communication tool. An email address is a kind of personal identifier, and email addresses printed on publications require persistent reachability. Kyushu University provides a university-wide email service, Primary Mail Service, and assigns a Primary Mail Address for each member. Divisions of the university additionally operate individual email services for their internet subdomains and administer member email addresses. Since email is a major means of cyberattacks nowadays, the secure operation of an email server demands considerable effort and high skill. This article describes a challenge at Kyushu University for consolidating individual email services. Since 2018, the Primary Mail Service has been operated using Microsoft's cloud service, Exchange Online, which supports multiple internet domains on a tenant. The approach employed is registering divisional subdomains to the tenant and configuring forwarding addresses from addresses of the subdomains to the Primary Mail Addresses or external addresses. A desirable scheme is for each domain administrator to manage forwarding addresses of the domain, but Exchange Online is unable to delegate administration to the domains. To overcome this, a system was designed and developed for domain administrators to create, read, update, and delete forwarding addresses. Beginning in July 2020, a new service to import divisional domains was offered. We are now planning measures for promoting the consolidation of individual email services.