The headers of an email contain useful information:
There are almost as many ways of obtaining message headers as there are email clients.
To obtain the headers of an email from your Roundcube inbox, follow these steps:
This will open a new window with the full message headers, which you can then analyze or copy and paste into a support ticket.
If your client is not listed on this page, just search the web for “how to view message headers in [your email client, i.e. Apple Mail or Thunderbird]”.