OIDC login disconnects after 5 minutes

[tziuhtli]

I am not sure if I should submit this as an issue. It might be that I just have misconfigured my instance. But I have an all-local setup:

1. A docker-mailserver instance with SSL enabled for SMTP and IMAP running on mailserver.mytld.
2. A roundcube instance running behind a caddy reverse proxy on roundcube.mytld.
3. An authentik instance running behind a caddy reverse proxy on authentik.mytld.
4. Everything resolves locally with the use of a local DNS server (this is irrelevant I think).

• All services are running on Docker. Including Roundcube.

Anyway, I configured OIDC on roundcube and mailserver using this guide and everything works except that after 5 minutes I get disconnected. Here are the relevant logs from roundcube.

<REDACTED caddy's IP address> - - [19/Aug/2026:05:36:44 +0000] "POST /?_task=mail&_action=refresh HTTP/1.1" 200 650 "https://roundcube.mytld/?_task=mail&_mbox=INBOX" "Mozilla/5.0 (X11; Linux x86_64; rv:154.0) Gecko/20100101 Firefox/154.0"
<REDACTED caddy's IP address> - - [19/Aug/2026:05:37:44 +0000] "POST /?_task=mail&_action=refresh HTTP/1.1" 200 650 "https://roundcube.mytld/?_task=mail&_mbox=INBOX" "Mozilla/5.0 (X11; Linux x86_64; rv:154.0) Gecko/20100101 Firefox/154.0"
<REDACTED caddy's IP address> - - [19/Aug/2026:05:38:45 +0000] "POST /?_task=mail&_action=refresh HTTP/1.1" 200 651 "https://roundcube.mytld/?_task=mail&_mbox=INBOX" "Mozilla/5.0 (X11; Linux x86_64; rv:154.0) Gecko/20100101 Firefox/154.0"
<REDACTED caddy's IP address> - - [19/Aug/2026:05:39:45 +0000] "POST /?_task=mail&_action=refresh HTTP/1.1" 200 650 "https://roundcube.mytld/?_task=mail&_mbox=INBOX" "Mozilla/5.0 (X11; Linux x86_64; rv:154.0) Gecko/20100101 Firefox/154.0"
oauth: <efaf6b10> DEBUG: [ip=<caddy's IP address> (X-Real-IP: <REDACTED laptop's IP address>,X-Forwarded-For: <laptop's IP address>) sub=e7221dcbf1eda9eca990be92d78527ad0907000082be37891dbd8ee70fe43fd4 ses=-] abort, no refresh token
errors: <efaf6b10> IMAP Error: Login failed for admin@mailserver.mytld against mailserver.mytld from <caddy's IP address> (X-Real-IP: <laptop's IP address>,X-Forwarded-For: <laptop's IP address>). AUTHENTICATE PLAIN: Authentication failed. in /var/www/html/program/lib/Roundcube/rcube_imap.php on line 197 (POST /?_task=mail&_action=refresh)

This is the custom configuration that I have on roundcube:

<?php
$config['use_https'] = true;
$config['oauth_provider'] = 'generic';
$config['oauth_provider_name'] = 'authentik';
$config['oauth_client_id'] = 'REDACTED';
$config['oauth_client_secret'] = 'REDACTED';
$config['oauth_config_uri'] = 'https://authentik.mytld/application/o/roundcube/.well-known/openid-configuration';
$config['oauth_scope'] = 'email openid profile';
$config['oauth_identity_fields'] = ['email'];
$config['oauth_login_redirect'] = false;
$config['oauth_cache'] = 'db';

$config['use_https'] = true;
$config['proxy_whitelist'] = ['REDACTED caddy's IP subnet'];
$config['trusted_host_patterns'] = ['roundcube.mytld'];

What comes to my eye is that roundcube says AUTHENTICATE PLAIN: Authentication failed but the authentication is done via oauth not plain. Any help is appreciated. Thanks.

[tziuhtli]

Found relevant issue #9364