[Bug]: Uppercase Letters in Email Addresses Cause Login and Email Delivery Issues

[reactor2k3]

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Subject: Bug: Uppercase Letters in Email Addresses Cause Login and Email Delivery Issues

Description:
When creating a user in Nextcloud with an email address that contains uppercase letters, the address is displayed correctly (with uppercase letters) in the account overview.
However, internally, the email address is saved or processed in all lowercase (or with uppercase letters removed).
This leads to the following issues:

Users cannot log in with their email address as expected.

Emails are sent to the "modified" (lowercase or shortened) version of the address, so users do not receive emails.

Steps to reproduce

1. Create a new user in Nextcloud with an email address containing uppercase letters (e.g., John.Doe@Example.com).
2. Check the account overview: the email address appears with uppercase letters.
3. Try to log in or send a test email:

Login via email does not work as expected.
Emails are not delivered because they are sent to the "shortened" email address.

Expected behavior

Either:

Only allow lowercase letters when entering an email address (validate and reject uppercase letters),
or

Ensure that all routines (login, email delivery, etc.) properly handle email addresses with uppercase letters, as per standard (email addresses are case-insensitive in the local part by most providers, but should not be modified).

Nextcloud Server version

31

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.3

Web server

Apache (supported)

Database engine version

MySQL

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

No response

[reactor2k3]

I also discovered a mistake in the German (Du) translation.

[skjnldsv]

Thanks for the ticket. I'll investigate!

Regarding the translations, they can be adjusted on transifex! :)
You can do it if you want or we can ping @rakekniven for a kind assistance 😊

[rakekniven]

Regarding the translations, they can be adjusted on transifex! :)

That typo has been fixed 13 days ago already and should be included in the next release.