This problem seems to persist to today - with version 1.0.0 - and attachments are not sent.
In one post:
"The maximum file size that can be attached in email via Rounbcube application is 20MB however, it is not sending email with attachment above 5MB size of file. While investigating, it appears that the issue is with the Roundcube application."
My server settings (SMTP & PHP) are configured for 20Mb max file sizes.
There are several posts about file sizes stored in the database - but remain unresolved.
Another post states that the temp directory is not writable - but it is, and is set to 777 and still doesn't send attachments. If there is a plugin that needs to be set or removed, which one? How? Is that set in the new (version 1.0.0) config file? There is no documentation.
There is also no documentation regarding how to edit/add settings for attachments in the new version:
$rcmail_config['plugins'] = array('plugin_manager','calendar','carddav','compose_in_taskbar','crawler','fancybox','folderbuttons','jscolor','lang_sel','persistent_login','placeholder','planner','plaxo_contacts','savepassword','timepicker','webmail_notifier','archivefolder','blockspamsending','zipdownload','message_highlight','database_attachments','contextmenu');
Thanks for any advice and suggestions to make this work!