completely SMTPUTF8 + IMAP4rev2 Support (RFC 6531 + RFC 9051)

[Ótzï]

Currently, no EAI email addresses (such as äöü@test.local) can be set up in Thunderbird, whether on a desktop or mobile device. Entering punycode is not a solution either, because EAI (SMTPUTF8) means native UTF-8, and there are no intermediate encodings such as punycode for IDN.

So the request is to support the setup of EAI email addresses with SMTPUTF8 addresses (So non-ASCII characters BEFORE the @).

I hereby request full support for IMAP4rev2 (RFC 9051) and SMTPUTF8 (RFC 6531) in Thunderbird, whether on desktop or mobile.

(The email addresses in the images do not exist, but that doesn't matter because you can't even get to the settings where ports/mail servers etc. are entered).

 

[Ógnijèn]

The current limitation forces users to create ASCII-only aliases or alternative mailbox names. That is inconvenient, confusing, and sometimes impossible in managed or organizational environments. Thunderbird should support the actual mailbox address instead of forcing workarounds.

[Fäysa]

This is important for universities, public institutions, companies, and international organizations. Many environments need mail clients that can handle internationalized identities correctly. Thunderbird would be a stronger choice for deployment if it supported EAI addresses properly.

[Sebastian234233]

Even if full support needs to be implemented in stages, this should be tracked as one complete feature. A useful first milestone could be fixing account setup validation, followed by SMTPUTF8 sending, IMAP UTF-8 handling, address book support, and robust fallback behavior.

[يوسف]

Please make sure this is not desktop-only. Thunderbird for Android and future mobile versions should support the same internationalized email addresses as Thunderbird Desktop. Users expect the same account to work across devices.

[אברהם2026]

This is also relevant for self-hosted and independent mail setups. Users who run standards-compliant servers should be able to use Thunderbird with modern email features instead of being limited by client-side validation rules.