Steps to reproduce

Hi so after the recent update to Mail I now can't get into the mail app in my Nextcloud instance. I already tried re-installing it but no dice.

What happens is I get a Nextcloud page the only says....

Internal Server Error
The server was unable to complete your request.

If this happens again, please send the technical details below to the server administrator.

More details can be found in the server log.

For more details see the documentation ↗.

Technical details
Remote Address: REDACTED
Request ID: A71Qnm3jp3Fv3JvuSle0

Checking in the logs I get about 15 entries of the same error log for index saying...

[index] Error: Certificate does not contain an email address
GET /apps/mail/
from REDACTED by USER at 20 May 2026, 15:39:17

Anyone got any ideas?

Expected behavior

Mail app loads

Actual behavior

Page loads that says...

Internal Server Error
The server was unable to complete your request.

If this happens again, please send the technical details below to the server administrator.

More details can be found in the server log.

For more details see the documentation ↗.

Technical details
Remote Address: REDACTED
Request ID: A71Qnm3jp3Fv3JvuSle0

Mail app version

5.8.0

Nextcloud version

33.0.3

Mailserver or service

Local Mailserver using SMTP and IMAP

Operating system

No response

PHP engine version

None

Nextcloud memory caching

No response

Web server

None

Database

None

Additional info

No response