EAI-Downgrading

(this is not referred to dictionary meaning but protocol part of Email Address Internalization).

Internationalization (UTF8SMTP) extension allows UTF-8 characters in SMTP envelope and mail header fields. To avoid rejecting internationalized Email messages when a server in the delivery path does not support the UTF8SMTP extension, some sort of converting mechanism is required. This is known as Downgrading mechanism for Email Address Internationalization. The entire protocol is now part of RFC 6530,31.

Note that this is a way to downgrade, not a tunnel. There is no associated up-conversion mechanism, although internationalized email clients might use original internationalized addresses or other data when displaying or replying to downgraded messages.

Downgrade Example:

If an email Email From UTF8 Compliant Email Server is sent having FROM email ID as যোগাযোগ@ডাটামেল্.ভারত (Bengali Script) and Recipient Email Server is not UTF8 compliant than sender SMTP should automatically follow downgrading and change from যোগাযোগ@ডাটামেল্.ভারত to Punycode. The downgraded of this email ID will look like ?utf-8?B?4Kav4KeL4KaX4Ka+4Kav4KeL4KaX?@xn--z5bd4bq1db8d6b.xn--45brj9c .

Workable Downgrading

There is also research going on to automatically covert EAI to a standard ASCII email address, instead of downgrading to encoded ASCII or punycode. Its also in practice by EAI Providers for using EAI address as display name while downgrading.