==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.6.2
- Deployed with iRedMail Easy or the downloadable installer? download
- Linux/BSD distribution name and version: Debian 11
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MariaDB (MySQL)
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? Yes
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

After migrating all databases from mail9 to mail10, everything seems to work OK _except_ the ability to log in to iRedAdmin-Pro. The login screen appears but after entering any username/password combination the result is always "Internal server error". Syslog isn't much help, as there's no specific error listed.

In this thread, zhb described running iredadmin as a standalone server, and having a curl client make a request to it:

https://github.com/iredmail/iRedMail/issues/85

That returns this error:

root@mail10:/etc/ssl/private# curl -k https://localhost:8080
curl: (35) error:1408F10B:SSL routines:ssl3_get_record:wrong version number

Usually that error is related to bad certs. This server has a valid Letsencrypt cert and it is linked to iRedMail.{crt,key} as described in the docs.

How can I troubleshoot and fix this internal server error? Thanks.