Sounds like there is a problem with your mime magic database file. I'm not sure on what options there are to fix that on FreeBSD but Roundcube does have config option to set a custom path to one if you need to:
// Path to a local mime magic database file for PHPs finfo extension.
// Set to null if the default path should be used.
$config['mime_magic'] = null;


Roundcube 1.7.4, php 8.3.33, FreeBSD 14.4

Roundcube is unable to attach files with certain extension to a mail (e. g. .png, .jpg, .svg). Other file extensions work just fine (e. g. .pdf, .docx, .xls).

Trying to upload a .svg file, for example, logs the following error. Errors for .png and .jpg look identical.

------
[09-Oct-2026 20:35:18 Europe/Berlin] PHP Fatal error:  Uncaught Exception: finfo::__construct(): EXTENSION type `               journal~' has bad char '~' in /usr/local/www/roundcube/program/lib/Roundcube/rcube_mime.php:745
Stack trace:
#0 /usr/local/www/roundcube/program/lib/Roundcube/rcube_mime.php(745): finfo->__construct(1040, '/usr/share/misc...')
#1 /usr/local/www/roundcube/program/actions/mail/attachment_upload.php(109): rcube_mime::file_content_type('/tmp/phpF8Txhh', 'test.svg', 'image/svg+xml')
#2 /usr/local/www/roundcube/program/include/rcmail.php(280): rcmail_action_mail_attachment_upload->run(Array)
#3 /usr/local/www/roundcube/public_html/index.php(266): rcmail->action_handler()
#4 {main}
  thrown in /usr/local/www/roundcube/program/lib/Roundcube/rcube_mime.php on line 745
------

Any ideas what could be causing this?

Cheers
sheep2045

Thank you, JohnDoh and SKaero - I understand that I have to consider cpanel to find an answer.
How can I set this topic to "Solved" or "Closed", or, will this be done by an Forum Admin?

Based on the path you gave to get to BoxTrapper "CP Webmail Home | BoxTrapper" that is most likely maintained by cPanel.

Roundcube is open source webmail client, cPanel uses Roundcube in there portal so you can view your email in the browser.

I see in Roundcube UI an informational text "cPanel". Could it be that BoxTrapper is handled by cPanel? And, if so. what is the relation between cPanel and Roundcube?

It looks like your provider BoxTrapper is using a plugin to add the functionality you are talking about to their installation of Roundcube. Please contact them for more information.

After Login to UI, I go to :
CP Webmail Home | BoxTrapper | Sperr-/Zulassungs-/Ignorierliste bearbeiten|Zulassungsliste bearbeiten
There, it is mentioned, that the entries use Perl RegEx.

If it works normally over mobile data or another internet connection but fails only when connected to Wi-Fi, look at the router/network path before blaming Roundcube. Roundcube itself is just the webmail interface; the actual connection still depends on DNS, HTTPS and the mail server being reachable. First try opening the webmail from another device on the same Wi-Fi. If everyone has the same problem, check the router's DNS settings and try a different DNS server such as 1.1.1.1 or 8.8.8.8, you can visit the settings page by typing your ip address such as 192.l.168.8.1 or 192.168.2.1 into the address bar. Also check whether the router or ISP is filtering the webmail domain or blocking the required traffic. If the webmail page opens but you get an error after loagging in, the problem could be on the IMAP/SMTP side instead. Roundcube can show connection errors when the underlying mail services or authentication are unavailable. The most useful test would be to compare Wi-Fi with mobile data. If the same account works immediately over mobile data, that points much more towards the Wi-Fi/router/DNS path than Roundcube itself.

If you dontt have access to the mail server, the available notification options are probably limited to whatever the webmail filter interface exposes. If you can change the subject but the body always stays as "Notification of new message", that usually means the notification template is controlled server side and cant be changed from the filter itself. Attaching the original message is similar. Some webmail systems have an option such as forwarding or redirecting the message instead of sending a notification, which would preserve the original mail and attachments. If your filter only offers "send notification", you probably won't be able to add the original message or create a custom body without a server-side change. so check whether there is a separate "forward" action in the filter options. If there isnt, youll likely need the mail administrator to change the filter/template settings.

you need to contact your email provider. roundcube is opensource webmail software you provider is using, it is not a service.