Email Address Internationalization (EAI) support in Office 365

Thursday, December 28, 2017
Today, Microsoft announced that Office 365 will enable Email Address Internationalization (EAI) support in Q1 2018. This may have important implications for hybrid customers and those organizations involved with mergers and acquisitions. Here is the announcement:
"Out of 7.6 billion people in the world, only 360 million are native English speakers.

Although email has been the earliest and most widely-adopted platform for modern electronic communication, email addresses have only supported a limited subset of Latin characters (mostly due to historical reasons). People who don't read or speak English have been forced to use email addresses containing characters not used in their own language.

Many people have been working together to try to fix this situation. In fact, new email standards to support email address internationalization (RFCs: 6530, 6531,6532, 6533) were published in 2012. However, changes in standards are difficult to implement in the world of technology due to the millions of legacy systems that are still out there.

Microsoft is pleased to announce that we're joining the effort to adopt the new standards. Office 365 will enable Email Address Internationalization (EAI) support in Q1 2018. As a first step, Office 365 users will be able to send messages to and receive messages from internationalized email addresses. Admins can also use internationalized email addresses in other Office 365 features (for example, mail flow rules that look for EAI addresses, or outbound connectors to Internationalized Domain Name (IDN) domains). But please note that this new release will not support adding EAI addresses for Office 365 users, or IDN domains for Office 365 organizations.  We will continue to evaluate these features as the standards are more widely adopted. We will also keep you posted on the plan to release this to Exchange Enterprise version."
As the article mentions, a change like this is difficult to implement due to millions of legacy systems out there - including Exchange Server on-premises, although I wouldn't call that "legacy". It's impossible to say how every email system will handle email addresses with "non-ASCII" character sets, but I suspect many will bounce emails as undeliverable.

Examples of EAI email addresses include:

  • Latin alphabet (with diacritics): Pelé@example.com
  • Greek alphabet: δοκιμή@παράδειγμα.δοκιμή
  • Traditional Chinese characters: 我買@屋企.香港
  • Japanese characters: 甲斐@黒川.日本
  • Cyrillic characters: чебурашка@ящик-с-апельсинами.рф
  • Hindi email address: संपर्क@डाटामेल.भारत

EAI support in Office 365 won’t matter for hybrid customers if Exchange Server on-premises doesn’t support it, since AD on-prem is the source of authority for email addresses. Microsoft says plans are being made to release EAI support for Exchange Server on-premises, but there are no release dates for this yet.

Organizations involved with mergers and acquisitions will need to be aware of EAI email addresses, especially in tenant-to-tenant migrations where EAI addresses are used. For example, if Contoso (an Exchange hybrid organization) acquires Fabrikam (an O365 tenant with EAI addresses), careful planning and reconfiguration of Fabrikam email addresses may be required.

It's also important to note that the EAI RFCs also permit the use of non-ASCII characters in email headers. This may have effects on various SMTP gateways used and may happen even if your own organization doesn't use EAI email addresses. You should ensure that your gateways are always updated. As usual, careful planning and testing is required.